knucklebone

One of two or more pieces of bone or wood held loosely between the fingers, and struck together by moving the hand.

Any of the joints between the bones of the fingers.

An old and evocative slang term for dice — the small numbered cubes used in gambling games. The name captures the deep suspicion that religious and moralist traditions held toward gambling: dice were literally the devil's tools, instruments of chance that could ruin lives and corrupt souls. The imagery of bones is doubly apt, since early dice were often carved from animal bones. Today the phrase surfaces in historical contexts, period fiction, and as a dramatic way to refer to dice in any setting.