Occasionally I get the darnedest questions at work. Someone wanted information about the toy The Magic Eight Ball, which used for fortune-telling or seeking advice,. It is apparently manufactured in China, and someone wanted to know if the number eight was selected – instead of seven or nine – because the number eight is considered lucky in China.
I found no evidence of that. I assumed it was developed from a billiards reference, which it appears to be. But it was interesting to read about the derivation of the term behind the eight-ball:
…a common idiom meaning to be in trouble, stymied or 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. 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.
Billiards historians… indicate that ascribing the phrase’s origin to the game of eight ball results in an anachronism, the phrase being traceable to at least 1919, while the form of game that became “eight-ball” was not described by that name, and its rules were not published in any official rule book, until after 1940.
You should read the whole section.
“Behind the eight ball” seems to be similar in meaning to the word snookered, referring to snooker, “a game played on a billiard table with 15 red balls, six balls of other colours, and a white cue ball. The object is to put the balls in a certain order.” Moreover, it is “a shot in which the cue ball is left in a position such that another ball blocks the object ball. The opponent is then usually forced to play the cue ball off a cushion.” In other words, in an awkward position. The term is from the late 19th century, long before the established color scheme of billiard balls.
Incidentally, there are several Magic 8 ball sites online, such as HERE and HERE and several other places; I will not vet the accuracy of ANY of them. A list of the possible answers can be found HERE.