Eponyms are names of people, real or fictional, connected to a product or place. They work in both directions, as it were: the waterproof boots called wellies are named after the Duke of Wellington; so the word wellies is an eponym of Wellington, and Wellington is the eponym of wellies.
The word eponym is also used loosely to describe something which is named after a place. Denim, for instance, comes originally from the French city of Nîmes.
photo by Lion Hirth (Prissantenbär)
Mind you, if you're going to use technical terms then you might as well be accurate as well, and call something named after a place a toponym.
Thing To Use Today: an eponym. This word comes from the Greek word epōnumos, which means giving a significant name.