http://www.microsoft.com/athome/security/children/kidtalk.mspx I actually did not know that w00t stands for ' we own the other team'
w00t isn't an acronym. It's used (and maybe originated) outside of online games. This sort of mistake happens every time the deciphering of youngster's colloguia is attempted ("you'd have to be crazy on acid to think a roach looks like a god damn cockroach"). What this article is missing is, "if your child appears to be using these terms, do us all a favour and throttle them with the nearest ethernet cable".
I wonder how Microsoft found out that one?! :-D Remember when people used to say 0wn, and not pwn? Those were the days... I wonder were leet really originated from? I probably heard it on good ol' Usenet before anything else.
Ascii-style talk (turning M into /\/\ etc) was present on BBS boards, from what I remember as a kid, so really it's probably about as old as multi-user text-based communication is; you'd be hard pressed to pin it down to even a particular year. And obviously it's changed a lot over the years as well...
I think in general it originates for example from BBS's or Usenet, where large nice pictures and stuff couldn't be used, they used clever things like other symbols to make letters and titles look nice.. So today it's rather useless for this kind of art.. And for the leet stuff... I read on a site (don't know if it's a trustworthy source) that it was used by coders to talk to each other over the internet withouth worrying that other people could spy on what they where saying.
That's BS, any idiot can understand and type in 1337 (in fact I'd say it was a requirement these days).