Although didn't the "official" designations all start out as fandom ones?
TOS, TAS, TNG, DS9, VOY, ENT, ...ALT?
When the old pre-Internet newsgroups and BBS were all we that we had, I recall "Star Trek Classic" (STC) being used by many fans to distinguish the original series from Filmation's animated series (STA). It hadn't been all that long since the USA had its New Coke vs Coke Classic
debates. About that time, David Gerrold was auctioning off cans of original Coke (not just Coke Classic) in SF convention charity auctions.
Then along came "The Next Generation". And STC seemingly morphed into the more catchy TOS, and STA became TAS, perhaps to conform with TOS.
So the concept of "nuTrek" may well have its roots in that. Trek Classic
vs New Trek.