Flea market
The origin of this term, which first appeared in English in the 1920's, most probably lies in Paris, where Le Marche aux Puces (literally, 'market of the fleas') was a popular shopping venue. Le Marche aux Puces took its name from the semi-humorous (and probably at least partly accurate) popular perception that the market's ragtag goods were more than likely to be infested with fleas.
The piece at the top of this post is my favorite. I believe it was a belt buckle of some sort. Maybe.