off one's chump

Etymology
See, and compare.

Prepositional phrase

 * 1)  Crazy, insane.
 * 2) * 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.’
 * 1) * 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.
 * It put him off his chump entirely. He went completely to the bad.