Buckley's Chance : No chance at all (or only a very slim chance). Also called "Buckley's and none" or "Buckley's hope".
The origin of the term isn't certain but the most popular story pins itto William Buckley (1780-1856), a British convict transported to Australia.There, he escaped and found refuge among the Aborigines for more than threedecades. When he was rediscovered he had forgotten how to speak English.Since survival in the outback was difficult it was said that anyone lostthere had Buckley's chance of making it.
Another possibility is a pun on the Melbourne department store Buckleyand Nunn, i.e. one has two chances: Buckley's or none