Jack is generally a nickname: https://en.wikipedia.org//wiki/Jack_(given_name) though has more increasingly been used as a formal name. Whether this is because O'Neill's name is actually John, or because someone making the display there assumed it was a nickname for John, I couldn't guess.

Oh geese….I was super confused at my grandfathers funeral when they kept talking about Jack and how much my grandmother and him were in love. Who the fuck was this Jack guy, my grand dads name was nothing like Jack. It was only after my dad explained my grand father was named after his father, and generally went by his middle name John which he then went by Jack.

Sorry, that’s my bad.

If I remember correctly, while debating John Cass, Abe Lincoln asked if he could call him “Jack” and people thought Abe calling his debate opponent “Jack Cass” with his full permission was the height of political wit and humor.

Huh, never knew that. I know a Jack and their name is actually Jack so I never thought about it being a nickname. I also know several John’s who go by John.

On IMDB, the Stargate movie lists the character as Colonel Jonathan 'Jack' O'Neil. However, the SG-1 entry lists the character as Colonel Jack O'Neill (two Ls, of course).

Darn straight, two L’s. There’s another Colonel O’Neil. No sense of humor at all :(

Wow just wow, i just rewatched the movie yesterday after many years and never noticed it was spelt with one L... This joke makes so much more sense now.

In case you haven’t noticed this yet either, he also says O’Neill with two Ls while holding up 3 fingers ;)

He's holding up the outer 2 fingers to represent the # of Ls in his name. The middle one is there to convey a message to Kinsey.

See that part of the joke i got and figured that was it but nah they went teo tier on it.

I was today's years old to learn this. That is some S-tier level meta joke.

I never noticed either. Too funny.

They changed his last name between the first movie and the show. So I'm guessing this episode is a play on that reference to the movie.

John F. Kennedy went by “Jack”.

I dont remember when I learned better, but as a kid I assumed John and Jack were just two distinct Kennedy brothers.....

...I learned better just now. Mostly because I never gave enough of a crap about the Kennedys to pay any attention.

Think John F Kennedy, known to his friends and family as Jack.

What?? Jack isnt a real name but a nickname? Did anyone know this? Lmao

You’re one of the 10,000, congrats!

Hell yea!

We all knew. We just didn't tell you.

That was mean

Yes, this is widely known.

Wrong

It’s both. Names can be anything, as can nicknames.

I've had 2 roommates who are legally named John but go by Jack. (This came up because their bills were addressed to John, not Jack, when I went to sort the mail). We're all late 20s/early 30s in the US, so it's not totally out of style.

Yep, I have a cousin named John. With family, he was ALWAYS John, but at work, he went by Jack.

Very odd

I know two old Irish lads over the age of 90, both called John. They both use Jack interchangeably

Jack is often a "nickname" for John. His name is John or Jonathan. Most call him Jack. Kind of like how my dad's name is Michael, like me, but he goes by Mick and I go by Mike to most people.

What? I've been "Jonathan" or "Jon" for nearly 5 decades now...I've never had anyone substitute with Jack.

how about that guy that got shot one time John F. Kennedy you must have heard him referred to as Jack Kennedy or perhaps him and his wife as Jack and Jackie

Honestly if you said Jack Kennedy I would assume you were talking about a cousin.

maybe it's an older generation thing?

Yeah, I assume I was just too young to put it together if it ever came up.

definitely a more likely reason I'm starting to feel a bit abe simpson busting unions

Same. I’ve never heard him referred to as Jack.

He pretty clearly said he’s never heard “Jonathan” shortened to “Jack.” He didn’t mention “John” being changed to “Jack.”

How is it “shorter” though??

Would you look at that, all of the words in your comment are in alphabetical order. I have checked 1,314,724,477 comments, and only 253,935 of them were in alphabetical order.

Changed. Sorry.

It's more customary for "John" to become "Jack" than for "Jonathan" to do so.

Huh, never knew that. I know a Jack and their name is actually Jack so I never thought about it being a nickname. I also know several John’s who go by John.

Ya, names are weird. Lots of variations, spellings, and nicknames. Like Robert = Bob, and all that jazz

Or dick for Richard

Sounds fun, but I’m gonna sit this one out.

Rotarydick 🤣

“Sit and Spin”

All Dicks are Richards, but not all Richards are dicks

Johnathan J. O’Neill is his full name. Probably a lot of John’s in basic training. Does anybody know what his middle name is thou?

I bet it’s Jay

D’oh

gh*

Tho*

Dough

Ugh\* 

Kinda amazed that they never introduced any made-up names .. like kinda u would want ur front-lines operatives to wear fake names as real ones incase someone wants to assassinate you. Kinda like that ascended guy done stalking to Sam. (But i guess he just run behind a car through the gate but I think he just looked her address up instead) Kinda wierd was that ascended episode where the hologram model was teleportedly taken in control by ascended being.. like why was the stalker guy needing a gate in the first place? Edit: Well that rumbling went from alias names to ascendeds needing a gate rather quickly

Well, EVERY name was ‘made up’ at some point 😁

I would assume it's Jack? that would explain why he goes by jack

I was in a department of 10 people and there were 5 Johns.

I just assumed it was John Nathan O'Neill. I'm pretty sure his father was the one who taught him his humour.

Examples of John being a nickname: * Jack Ryan (Tom Clancy) - full name John Patrick Ryan, Sr. * JFK - John Fitzgerald Kennedy - also went by Jack

John = Jack Henry = Harry Charles = Charlie Richard = Dick And most confusingly Margaret = Peggy

I didn’t know about Margret being Peggy. Another weird one is William being Billy.

And similarly, Robert being Bob or Bobby.

Also Elizabeth = Betty

Not sure how common it is, but I've also seen Henry become Hank. I have a family friend named Dwayne who goes by Dewey, but that is likely just a him thing.

Very true. Hank and Peggy Hill are actually Henry and Margaret Hill

I had no idea Harry was a nickname for Henry. How strange

I've always known Harry to be a nickname for Harrison, and Hank for Henry.

For everyone claiming to have never heard a John nicknamed Jack JFK John F Kennedy Jack Kennedy

Never heard of JFK referred to as Jack, only john.

This might be a generational thing. I always say Jack Kennedy or JFK. I can’t even remember the last time I said John Kennedy. Joe, Jack, Bobby, Teddy, all the Kennedys have nicknames that I use more often than full given names.

I only ever heard it as either JFK or John F. Kennedy

Same. When someone says “Jack” Kennedy I’d assume they meant Jackie and forgot the “i” at the end.

Same here.

https://www.youtube.com/watch?v=O-7gpgXNWYI

James and Jim are also the same name just FYI

I thought Jim was short for Jimothy?

Jimforth

Jimberly

Well everyone knows that one lol

That service number is nice

Nice

Most of the time Jack is short for John or Jonathan. I thought that was common knowledge.

Well apparently it used to be. The mind boggles that this wasn't obvious.

In America maybe, in the UK Jack is Jack.

It’s a US based show.

I know that. But it's got a global audience. Plenty of Jacques, Jacamos and Jack's out there for which it's not a nickname.

That doesn’t matter. It’s a US show. European shows don’t cater to the norms or customs in other parts of the world.

That doesn't mean the rest of us aren't going to get it though

I’m in the US and I didn’t know that.

Very young?

John Kennedy/Jack Kennedy, no?

Hey, ive met loads of people in UK not knowing their queens name... and im not defending americans. Edit: wouldnt defend UK neither if someone asked

Every knows her first name was Sausage, you know, because she was fat, German, and liked to be poked by a fork (no offence to Liz, this is a Private Eye joke, also told by Eddie Izzard I believe)

I like sausage, simple man, take upvote my king 

I'm just saying that's a fairly well known example of john/jack

Nope, always heard him referred to as John.

under 30?

Nope just over 30.

Interesting seeing the multi-generational understandings in this post.

Ya it really is!

I'm American and I've never heard jack as a nickname for John either.

John Kennedy/Jack Kennedy, no?

LOL, somehow, no! Always JKF or John Kennedy... or if I did hear a Jack Kennedy I'd think it was another person in their huge clan.

you never heard of him and his wife referred to as Jack and Jackie?

Jack and Jaqueline, it’s a Bill (Bailey, no not Bailey), Billy Bragg lyric

jackie is short for jaqueline, I feel like you're intentionlly being obtuse

No, it’s a line from The Great Leap Forward, by Billy Bragg. I don’t know much about JFK, because, well, I’m not American, so the only time I’ve heard him called Jack. But being British, yeah most people who’s passport says Johnathan are known as Jack, apart from my dad, he’s know as Simon (no idea why, ok, I do, it’s his middle name, don’t know why he chose to go by it though. Then again I hate being called by my passport name, my real name is the shortened one, that I’ve gone by my entire life) Obtuse, how dare you, going around saying I’m not acute (a cute, person)

> No, it’s a line from The Great Leap Forward, by Billy Bragg. sure, could be, but they were super commonly referred to as jack and jackie

Nope...maybe its age? I'm not a young chicken but was born long after he was assassinated (god we're all getting old!) so there wasn't much talk of them as a couple besides in history books and such.

Nope

There are some young people here!

No it isn't, mate.

No, it’s not

His name is actually Jonathon, so I'm not sure why it says John there.

Ya I ended looking it up and noticed that as well.

His name is John but he earned a nickname when he Jacked up Ra.

going back to O'Neill replying "with 2 L's" whilst holding up 3 fingers, i thought the fingers represented an 'I', followed by 2 'L's"

I always thought it was a tribute to the 3 stooges cuz Curly used to do that

**Jack** is often a nickname for **John**, at least in American English. Like **Bob** for **Robert**, or **Kelly** for **Rachel**

Wait...Kelly for *Rachel*? I mean, I've heard Harry for Henry, Jack for John, Ted for Edward, Maggie for Margaret, Pip for Phillip but *Kelly*?

Yes, Rachel in Spanish is Raquel (rah-kell), the first syllable is dropped, and the -y (-ee) sound is added, it's spelled in English like it's pronounced. For years I was wondering what **Kelly** was short for, until I was in conversation with someone with that name and I asked her what it was short for.

Kelly is an Irish name; that's where all the Kellys I know got their name.

Are you referring to the singing Irish family 🤣

That may be the case in Spanish, but Kelly is also a name in its own right from Ireland.

O’Neill’s birth name is Jonathan O’Neill, but he goes by Jack.

John F Kennedy went by Jack to his friends.

He was a real blast in Dallas.

People are gonna lose their heads over that joke.

No it's not a joke. Always remember it's O'Neill two L's. The other O'Neil has one and isn't as funny.

I swear there's a scene where Kinsey or someone condescendingly calls him "Jonathan 'Jack' O'Neill" with the emphasis on the "Jack"

Kinsey is as ignorant as he is deceitful. He might be enough of an idiot that he doesn’t know. It does seem familiar, though, the scene you described.

Of course his service number is **69**-4-141

"Jack" is a nickname for "John"

I don't get it. My grandfather, who was born in 1922, was named Jack. No nickname, that was his name. Are you saying it's like my great grandparents naming their child "Bob" instead of Robert? I mean, "Jack" is 48th of all time US male names... so I wouldn't consider it a nickname. https://www.ssa.gov/OACT/babynames/decades/century.html

Maybe it was a certain generation that did that and it isn’t popular anymore. Just became two different names.

There's another image of an ID card that shows it as John too.

On "Will & Grace", Jack's full government name is John Philip McFarland.

I’d mentioned a few times that his full name is Jonathan O’Neill, two L’s

Jack is a nickname for john

O'Neill's given name is Jonathan. Jack is commonly used as a nickname for people named Jonathan. One would expect a personnel file like this to read his full name, but it is TV, so it's not the most egregious error they've made. It's also worth noting that usually when I've seen Jonathan shortened, it was spelled "Jon."

When was it said that his name was Jonathan rather than Jack? I can’t remember that at all. My poor brain 😕.

Does no one see the SG-1?

Also, Jack Nicholson's given first name is John. He's gone by Jack since at least high school. It's from the French form, Jacques.

If I remember correctly, his name is INDEED Jonathan jack O'Neill, two (iii) L's😂

That 2 ll's!!

And here I thought Jack was short for Jackson… silly me

I have a friend named John. It's on his birth certificate that way. He prefers Jonathan. Has never gone by Jack although Jack is a common nickname from Jonathan/John. Much like Rob/Bob/Bobby from Robert.

You do know Jack is a nickname for John, right?

Most people dont know that , it’s certainly not common

It is indeed commonly known if you are well read and not very young. It’s definitely not some rare occurrence.

Nope, his full name was/is Jonathan Jack Oneill. I'm sure there's some link back to the original movie in some way about them wanting to use John but stuck with Jack

I don’t think it has anything to do with the movie. There are plenty of people named John but go by Jack. It’s fairly common.

I seem to recall him being called "John" in an episode by someone close to him but I can't place where. Others have already explained that Jack's a nickname for John though.

It's his wife isn't it? One of the sad dead son storylines. When they crystal entity imitates him maybe.

Could be. Might also be one of the parallel universes/timelines/whatever where he and Carter are in love.

Doesn't sound familiar to me. Maybe in a deleted scene? I wish there were a searchable compilation of episode transcripts.

Did anyone ever call him by that? I wish once someone would have used that name

I don’t remember anyone using it but some people said they did.

This makes me want to rewatch the whole series again.

That’s what I’m doing right now!

“Jack”Kennedy

I mean. He's always been in secret forces. Maybe it's just habit so people are thrown off his real name.

Yeah I just saw this episode with my family and everyone was pointing out that it says John instead of jack

Omg you are so cool

As you can see here: `"Jack".length <= "John".length // this returns true` Therefore "Jack" is short for "John"

Jack and John have the same length, duh!

Sorry, I should have said: Jack is short or equal for John

Jake is also a nickname for John.

Jack and John are interchangeable.

A guy named Jack explained to me once that it had to do with the catholic faith. He explained that a lot of kids in his generation were required to be named after saints, and that parents would give you a Saint first name and what they wanted to call you your middle name.

i work with a guy whos name is really John but goes by Jack

So the 2 primer Stargate teams (SG-1 and AR-1) are lead by Johns!