Fire thief, derived from the Greek "pyro" meaning fire and "kleptein" to steal.
Some one who steals fire, generally in regards to a lighter
Bob: Hey Jones, can I borrow your lighter
Jones: Yeah hold on, here you go
Bob uses the lighter and then places it in his pocket....
Jones: Hey, you stole my fire you thief, don't be such a pyrokleptic
Actually this word developed because a past girl friend...a she who shall not be named variety ex-girlfriend, had a really bad habit of borrowing your lighter and then putting in her purse....