Good question. I think if you declared that instead of saying "red", we now all said "butterfinger", it's not that it would be illegitimate, but if it didn't g

Good question. I think if you declared that instead of saying "red", we now all said "butterfinger", it's not that it would be illegitimate, but if it didn't gain any momentum you'd be hard pressed to say that it was part of the language. However, the appropriation of jawn (which is implied to be working class vernacular) by white hipsters or whatever the original comment said could cause some consternation, but if it catches on, than I'd argue it's now just part of the language (what I called 'legitimate' in my original post).