I should coco/cocoa
Rhyming slang for I should say so, I should cocoa/coco meaning I should say so. Some maintain that the spelling should be Coco, after Coco the Clown, others say it is cocoa. Probably, cocoa was first but then Coco became more popular when Coco the clown, Nikolai Poliakoff, became famous after WWII. I should cocoa or coco dates from the 1930s.