off one's onion

English

Prepositional phrase

off one's onion

1. (slang) Crazy; insane.
   • 1913, Arthur Conan Doyle, “(please specify the page)”, in The Poison Belt […], London; New York, N.Y.: Hodder and Stoughton, →OCLC:

     "'E's a very clever man, the master - so clever that 'e's clean balmy sometimes. I've seen 'im right off 'is onion, and no error."