also wish-bone, 1860, from wish (n.) + bone (n.); so called from the custom of making a wish while pulling the bone in two with another person. The wishbone breaking custom dates to the early 17c., when the bone was a merrythought.

"wishbone of a fowl's breast," c. 1600, from merry (adj.) + thought. So called from the sport of breaking it between two persons pulling each on an end to determine who will get a wish he made for the occasion (the winner getting the longer fragment). Also see wishbone.