Definition & Meaning of "loony bin"in English

What is the origin of the term "loony bin" and how is it used?

Loony bin is an informal slang term that appeared in early–mid 20th-century English for a hospital or institution for people with mental illnesses. "Loony" comes from lunatic, an old word based on the belief that the moon affected the mind, and "bin" is used casually to mean a place where people are put. The phrase was never medical; it came from everyday speech and dark humor. Over time, it took on a mocking and dismissive tone, suggesting chaos or foolishness rather than care or treatment. Today it is considered insensitive and disrespectful, and it's mainly used jokingly, insultingly, or when discussing outdated language, not in serious or clinical contexts.