According to some theories, how did flea markets get their name?

A flea market (or swap meet) is a type of street market that provides space for vendors to sell previously-owned (second-hand) merchandise.

While the concept existed in places such as what are now India, Bangladesh, and China for millennia, the origins of the term "flea market" are disputed. One theory maintains that "flea market" is a common English calque from the French "marché aux puces" which literally translates to "market of the fleas", labelled as such because the items sold were previously owned and worn, supposedly containing fleas. The first reference to this term appeared in two conflicting stories about a location in Paris in the 1860s which was known as the "marché aux puces".