While you'd be right in the obvious thinking that this has something to do with being run over with a stiff metal comb to remove tangles, that's not what the "common" lexical meaning is;

In modern Western society, it more commonly means being asked for some sort of identification, proof you are what you say you are. This takes place in a lot of places for a variety of reason, the most common is to prove your age and to prove your name.

A good example is showing a Driver License to get into a 21-and-older Social Club, or showing a State ID card at a bank when withdrawling money from an account to prove you are the holder of that account.