Here are some terms associated with places. In each case something about the term is misleading.
German silver: A white alloy consisting of nickel, zinc, and copper originally obtained from an ore found at Hildburghausen. The product is German, but contains no silver.
Hudson seal: Â Muskrat fur that has been plucked and dyed to give the appearance of seal fur. The fur is from Hudson Bay, but it’s not from a seal.
Jordan almond: an almond imported from Málaga and used extensively in confectionery, or an almond coated with sugar of various colors. The almonds are not from Jordan and never were. “Jordan” in this expression is an altered form of French jardin, “garden.”
Pennsylvania Dutch: people living mostly in eastern Pennsylvania whose characteristic cultural traditions go back to the German migrations of the 18th century. The German word Deutsch predictably became “Dutch” in American mouths, but at one time in English, “Dutch” referred to Germans in general. In the 17th century “Dutch” narrowed in meaning to “of the Netherlands.”
Irish potato: the white potato (Solanum tuberosum). The white potato came to Europe from Peru. It became permanently associated with Ireland because of the dreadful Irish Potato Famine (1845-1852) during which a million Irish died and a million emigrated. Ireland wasn’t the only European country to experience a potato blight at that time, but a third of the Irish population depended entirely upon the potato for food.
Wow. There are a LOT of these expressions. I don’t know of a collective term for them, but there probably should be one, espcially for those in which neither of the terms in an adjective noun construction is accurate. E.g.
Guineau pigs are not related to pigs and are not from Guineau.
Peanuts are not nuts, and are only thinnly related to peas.
Also, think of all the herbal “teas” out on the market that contain absolutely no tea whatsover. They are really infusions- -which of course wouldn’t move them from grocers’ shelves at all.