Ringworm is a skin infection that makes red, itchy rings, often on the body or on the head. On the head it can make hair break or fall out in patches. The name sounds like a worm, and the red circles look a bit like a worm curled into a ring — but there is no worm in the skin at all. It is caused by a fungus, the same kind of living thing that can cause itchy feet. You can pick it up from people, from pets, or from damp floors. Doctors treat it with cream or medicine, not by “taking out a worm.” The word is ordinary and a little medical; it is not rude. Though actually, English already used a word like this many centuries ago for a worm in the gut, and later people used the same kind of name for the skin illness because of the round marks.

癬、金錢癬；長在頭上的叫頭癬。不是真的有蟲。