off one's chump

== English == === Etymology === See chump (“the head”), and compare off one's head. === Pronunciation === === Prepositional phrase === off one's chump (British, Australia, colloquial) Crazy, insane. 1888, Rolf Boldrewood (Thomas Alexander Browne), A Sydney-Side Saxon, Gutenberg Australia eBook #0607291, ‘ […] I′m not off my chump, no more than you are, and I haven't smelt spirits since last Christmas.’ 1890, Catherine Martin, An Australian Girl, 2002, Margaret Ellen Allen (biographical information), Rosemary Campbell (introduction and notes; editor), University of Queensland Press, page 90, It put him off his chump entirely. He went completely to the bad.