This post shows a sarcastic take on the phrase in alt.music.alternative, and predates only slightly the first solid use of whoot as a geeky slang interjective in the subject-line of this alt.cyberpunk post on Aug 8, 1993:

The term, woot, was in use in Middle English literature to mean "know". The term can be found in line 849 of Geoffrey Chaucer's The Wife of Bath's Tale: "For wel I woot thy pacience is gon.." ("For well I know your patience will be gone"). [2].

Leet (written 31337, 1337, and l33t), or Leetspeak, is a written argot used primarily on the Internet, which uses various combinations of alphanumerics to replace Latinate letters. The term is derived from the word "elite", and the usage it describes is...

After that there are more appearances of the same phrase in the sports context and increasingly as a standalone phrase in more "geeky" settings. July 11 1993 in rec.games.frp.dnd saw whoot in a DND gamer's sig:

Internet slang

The term "w00t" (pronounced, and sometimes spelled, "woot"; IPA pronunciation: [wuːt]) is a slang interjection used to express happiness, excitement or joy, most often expressed via the Internet. The expression has been used in Usenet posts [1], multiplayer computer games (especially first-person shooters), the IRC and SILC chat protocols, instant messages, weblogs, and web forums.

w00t is also said to be an abbreviation for "We Owned the Other Team", but this is a backronym. The current use of w00t on the Internet traces its origins back to a popular culture reference from the early 1990s. In 1993 two popular songs with similar titles and themes both rose to the top 10 of Billboard Magazine's Hot 100 popularity chart for the year. "Whoot, there it is" and "Whoomp, there it is" by rap groups 95 South and Tag Team, respectively. In both the term was used as a "wolf whistle" at the sighting of a voluptuous woman's posterior (which followed in the footsteps of the previous summer's #3 smash hit "Baby Got Back" by Sir Mix-A-Lot). The popularity of these songs and the phrase quickly spread to the internet in discussion of the songs and in similar discussion in alt.rap and rec.music. However, the phrases were catching on in a larger context, as in this post about "whoot" from rec.sport.basketball.pro (nb. the citation of the Chicago Tribune newspaper):

The link to Doom is interesting, as Doom itself appeared in 1993 -- the same year as the popular "whoot" rap songs -- and included a multi-player mode where players could type messages to each other during gameplay. The "w00t" form would have been faster to type, and of course more l33t. As the term began to be used in geek settings, it has been proposed that the word gained popularity as a term for "root access." Hackers often communicated using code words to signify their progress on the machine they were attempting to compromise. The code word for root access to a PC was woot, and because of the difficulty in obtaining root access, w00t was used in a celebratory manner. "Woot!!" is also a commonly used term in MMORPGs (massive-multiplayer-online-role-plaing-games) or RPGs (role-playing games) in general to shorten the phrase "wow loot" or 'wondrous loot' thus "woot". This term is thus associated with happiness or joy because it denotes the finding of significant wealth, treasure, or items which are desirable.

"W00t" was among the list of Merriam-Webster's Words of the Year for 2007.^[1] According to Merriam-Webster's president, John Morse, "w00t" was an ideal choice for the Word of the Year because it blends whimsy and new technology.