john
Synonym discussion
Sense: noun/1
For sense 1, john is a very informal American word for a toilet. Bathroom and restroom are the everyday polite choices in North America, especially when you ask where one is. Toilet is more direct and names the object itself, so it can sound blunt in some social situations. Lavatory is more formal and often appears on planes, in public notices, or in older British-style wording. John usually sounds casual, rough, comic, or slightly old-fashioned. If you are speaking to strangers, restroom or bathroom is safer; if you are reading dialogue, john often signals relaxed speech.
Etymology
The toilet sense probably grew from older American slang such as johnny house, an informal name for an outdoor toilet. The personal name John later also became slang for a man who pays a sex worker. The two modern senses are both informal, but they belong to different social settings.
First known use
1906
1906, in the meaning defined at sense 2 Noun (2)