There's a group of words — I think they're called determiners — used to indicate number in some way... like many, few, most, etc. During a linguistics class my professor said this was a closed group of words, and that new ones couldn't really fit in it. Then someone shouted out "There's mad people in here!" and everyone laughed. (Mad meaning many, the usage I'm referring to).
How did mad come to fit in this supposedly closed group? Are there other words that were newly coined to fit there?