UrbanDictionary.com has several definitions of the term. It may or may not have originated on GameFAQs, Something Awful, and/or Starcraft, and it may or may not have something to do with the Korean word for “fuck you”.
Personally, I always just figured it was a way to mock Internet acronyms, but whatever. Also, I think saying BBQ stands for “be back quick” is BS. It’s barbecue. I mean, come on.
I’m not sure when I first heard it (thanks a lot, apartment fire, for destroying my records), but I know it was Kevin who first said it to me.