I should cocoa (or coco) used to express scornful rejection of a ridiculous suggestion. British slang
☞Cocoa is short for (the fairly rare) rhyming slang coffee and cocoa 'say so'. The phrase was popularized in the 1950s by the BBC radio programme The Billy Cotton Bandshow.
2008Andrew SangerJ-Word Do they show you that you are appreciated? Do they make things as easy for you as they possibly can? Do they heck. I should cocoa.