The remark cited in the heading has been a standard flippant answer for at least ten-twenty years. A friend says that it first became a catch phrase after being used in a movie, but she doesn’t know what movie.
Can anyone given a cite?
The first movie I recall hearing it in was Top Gun (1986). http://www.imdb.com/title/tt0092099/quotes
Charlie: Excuse me, Lieutenant. Is there something wrong?
Maverick: Yes ma’am, the data on the MiG is inaccurate.
Charlie: How’s that, Lieutenant?
Maverick: Well, I just happened to see a MiG 28 do a…
Goose: We!
Maverick: Uh, sorry Goose. WE happened to see a MiG 28 do a 4g negative dive.
Charlie: Where did you see this?
Maverick: Uh, that’s classified.
Charlie: It’s what?
Maverick: It’s classified. I could tell you, but then I’d have to kill you.
And yes, it is rather sad that I remembered that. I know it is. I have nothing to say in my defense, other than it was on TV one weekend afternoon last month. I’d already seen Trading Places etc, so no point in watching the repeats. The choice was a Lifetime movie, Top Gun, college football or absolute drivel.
I saw it as a joke in the 80s sitcom Cheers, but I can’t say if it predates the Top Gun usage.
Slipster are you actually posting in GC expecting someone to answer that question? I mean, I could tell you, but then I’d have to kill you. 
If you killed him, would you use a 1920’s Style Death Ray? 
can’t help with the origin, but I sure do wish it would go away.
The reality is more like “If I told you, you’d have to sign an NDA and I’d be in trouble.”
Not quite as macho, is it?
I heard it well before Top Gun came out. It may have started with an earlier movie.
Yes, I am currently inclined in that direction, yes thank you.
Didn’t Colonel Flagg say it on MASH?
My mind immediately raced to a Get Smart episode…I’m getting old
I’ve found it best to use two 1920’s death rays, and load one of them with blanks.
Cool point. That way, I wouldn’t know which one of me killed him.
Exactly. The quote is a joke!
I can’t tell you how many people appear to take the statement at face value.
(i.e. “How deep do submarines go?”
Ans: “Sorry–I could tell you, but then I’d have to kill you.”
“Oh, never mind, then.”)
:rolleyes:
If I killed you, I’d have to tell you. That’s something to consider. In an intergalactic interethic frame of reference, that’s indeed something to consider. Googlistically speaking, morally speaking (I would not speak morally,) evil does not beat pure profit. Any tangents are in error
I first heard it on an episode of “Home Improvement” in the early 90s, for what that’s worth.
But of course, that’s long after the Top Gun usage, so it’s pretty much useless in determining an original coining date. So it’s just FYI.
I first heard it on an episode of “Home Improvement” in the early 90s, for what that’s worth.
But of course, that’s long after the Top Gun usage, so it’s pretty much useless in determining an original coining date. So it’s just FYI.
I first heard it on an episode of “Home Improvement” in the early 90s, for what that’s worth.
But of course, that’s long after the Top Gun usage, so it’s pretty much useless in determining an original coining date. So it’s just FYI.
It’s a standard* magician’s* aswer to the question “How’d you do that?”
How’d you do that?
I could tell you but I’d have to kill you.
Okay. Just tell my wife. 
I first heard it when I worked in an environment that required security clearances. There’s the old device in movies about the person who had to be killed because “he knew too much”. Someone had information about something – a secret weapon or a plot or something – that would be dangerous to the conspirators if it were found out. For example, a scientist might be involved in building a super-weapon. Being a scientist, he might be doing it because it fascinates him; but he’s not expecting it to actually be used offensively. Being of this temperament, he is a liability to the “organization”. Killing him would keep him from spilling the beans. So “If I told you, I’d have to kill you” means "If I told you about this thing, then you would know too much and you would have to be eliminated.:
The Man Who Knew Too Much was released in 1934, so that phrase must have been fairly well known long before then. When did “he knows too much” become “If I told you, I’d have to kill you”? I don’t know. But the literary concept has been around in films and books for a long time. The military concept has probably been around since Grup wanted to keep Egah from disclosing the location of their berry bush.