The other guesses were: CDE - Common Desktop Environment, MTC - Missionary Training Center.
GPT is much better than web search for this, I'll say that. It's ability to use context is invaluable.
GPT is useful, but there's an annoying tendency of it's proponents to promote it with examples they haven't validated.
> UUG is an acronym for: Uniface Users Group. Universal Underwriters Group. Unix User Group.
This user group was already in place by the time Linux came along, so you had the UUG doing Red Hat boxed set giveaways and such. There was a ton of excitement about Linux and not as much about Unix at that point. Then a bit more proper-Unix excitement when OS X came out.
The other ones are correct.