Crapper is a rude, informal word for a toilet — the bowl, or sometimes the room. It is built from crap (a rude word for poo) plus -er: 'the thing you use for that.' People also say in the crapper to mean in serious trouble. You will hear it in casual American and British speech, never in a textbook or a polite request. Though actually, a famous story says it is named after Thomas Crapper, a Victorian plumber whose company made toilets. His name is real, and soldiers in the First World War may have joked about his fixtures, which perhaps helped the word spread — but the word itself comes from crap, not from his surname. That surname Crapper comes from an old dialect form of cropper, a farmer, which is a different path entirely. Do not tell the story as if the toilet were simply named after him.