fid

underage kids who are texting each other and do not want to risk spelling out "fake I.D." in their messages use the shorthand "fid"

Do you know where I can get a fid at this school?
She doesn't have a fid so don't ask her to buy for us.
Yeah, Mark and George have fids so they are buying alcohol for the party this weekend.

Only invite people that have fids to go clubbing tonight.