'w00t' is "Merriam-Webster's Word of the Year 2007", which in itself is a little sad,
but not as sad as their bogus etymology they try to pass off as dictionary-
worthy.

'w00t' was never an acronym.  I don't know who made that up -- the best hope for
M-W is they asked someone who *should* know, and that person naturally told them
something ridiculous as a way of messing with the squares.

'w00t' did not first become popular in "competitive online gaming forums".
'w00t' existed long before 'gamer' became an epithet anyone would willing
self-identify as.

For my money the premier site for early online history is Jason Scott's 
fabulous textfiles.com.  A quick search of the collected wisdom of the internet age
reveals the term 'w00t' was cliche as early as 1995 (but certainly well before then.)

You can find documents that hint at what I believe is the word's true origin: 
a l33t corruption of the term root. Two examples include the "Hacking Kit Version
2.0.b by Invisible Evil (March, 1997)" and this "Hackers Information Report", circa 1999.
(There is also a very funny, though equally bogus etymology of 'w00t' linking the term 
to Discordianism.)  Nothing about gaming, for those keeping track.  You can also 
see it being used as "an expression of joy" divorced from any direct reference 
to hacking -- the mass popularity of "competitive online gaming" has not 
changed the term in this regard.

Score: +1 for the hackers, +1 for my nostalgia, and -10000000 for
academic research and Merriam-Webster.▒