On a recent episode of Top Chef Masters, I hear one of the cheftestants describe the ingredient sea cucumber as "a slug". Which, of course, is patently incorrect. There are such things as sea slugs, which are mollusks, but the sea cucumber is an echinoderm, which makes it a closer relative to the starfish than the clam.
Well, at least she didn't call it a vegetable ( never mind that cucumbers are botanically a fruit). Ingredient names are funny things.
Take for example that the peanut isn't a nut. Nor is a black eyed pea a pea. A geoduck isn't a duck (and the word isn't even pronounced the way it reads). The etymological confusion goes beyond ingredients to actual dishes. Like the way a Welsh rabbit doesn't even have meat in it. Or that an egg cream has neither eggs nor cream in it.