Fun With Collective Nouns

As an avowed grammar nerd, there are few things I like more than collective nouns. I love that they run from the whimsical -- a "charm" of hummingbirds -- to the morbid -- a "murder" of crows -- to the just plain strange -- a "rhumba" of rattlesnakes.

My question, which a five-second perusal of the Internets failed to answer, is who gets to decide when one of these things enters the lexicon? I mean they're already words, right? If I just start calling every group of car salesmen I see a  "cancer," and enough people pick up on it, does that get to be a collective noun? Or is there some secret society of English professors in a remote dungeon somewhere that approves these things? These are the sorts of questions that trouble men's souls.

Anyway, I've been pondering a few new ones, and once I figure out the process, I'll be submitting them to the collective noun tribunal, or whatever it is.

- a "Pabst" of hipsters
- a "shrill" of tweens
- a "Zima" of sorrority girls
- a "date rape" of frat boys
- a "Prius" of non-profit workers