The two women coming down to the river suspect they're whores because they aren't wearing "wimples", which would've seemed incredibly slutty at that time in France. Like fishnets and a leopard print miniskirt.
A wimple was a large piece of cloth worn around the neck and chin, and covering the top of the head. Some nuns still wear them nowadays. They were sort of like the Hijab Muslim women wear, but were really more of a cultural rather than a religious proscription. Their usage ebbed and flowed in different areas of Europe from the eighth to the fourteenth century.