You—as in you, personally—don't have to prove a thing. However, in the context of the history of TTRPGs and the terminology associated with it, determining the origins of this term is important, and in that, scholarly rigueur is required. Most of of here that think that this is a topic worthy of research agree that a wider net needs to be cast if we want to collaborate (or reject, if the evidence isn't there) hearsay.
While I agree that non-internet sources need to be searched, I find that your premise that lack of pre-2009 (not, 2000, as you state) internet results doesn't discount widespread non-internet usage to not be compelling. TSR and other gaming companies already had an established footprint on the internet in the early/mid 90s. By 2000 (and the advent of 3e and Erich Noah's original website), TTRPG gamers had already created established communities beyond AOL and Usenet. If a term was widespread at that point, it beggars belief that there is no evidence of it in any TTRPG community prior to 2009. You're essentially saying that it was widespread, but no one used the term (or at least in uncontracted form) in online conversations before 2009 for reasons and that it wasn't until 2013 that, for reasons, that gamers decided that it was okay to now use.