"Behind the eight ball" (or "behind the eight") is a common idiom meaning to be in trouble, stymied, thwarted, in an awkward position, or out of luck. It is often assumed that the expression derives from the inability to use the 8 ball in a combination in the game of eight-ball—if the cue ball is directly behind the 8 ball a player has no direct shot route. However, numerous billiards-specific and etymological publications state that the expression derives instead from kelly pool, or an early version of kelly pool called kelly rotation.