Wikipedia has an interesting article on this word. Interesting snippets:
- It is an unusual English language word in that it is one of the few words of seemingly unknown origin that is not considered slang in contemporary usage.
- Its use is found almost exclusively in North America, and has been said to have been first widely publicized in communications between the astronauts and Mission Control of the Apollo Program in the 1960s
- It's in the OED, so you know it's a real word... :)
- David Mamet has written an article about its origins, although perhaps in jest.