Craps is a game in which players make wagers on the outcomes of rolls of dice. Because dice tumble randomly and the outcome is not predictable, craps is a game of chance. From this we can infer the meaning of the metaphorical term crapshoot—that is, a situation whose outcome is not predictable.
Crapshoot is a new word. The earliest examples we can find are from the 1960s, but it was not widely used until the ’80s. Even today it is still primarily an Americanism, though a few scattered examples are easily found in non-U.S. sources.
The game is craps, not crap, yet the term is often spelled crap-shoot or crap shoot, and it’s almost never spelled craps shoot. The one-word crapshoot helps us get around the spelling issue because we can just say the extra s was dropped in compounding. The one-word form appears about as often as the two-word forms.
Shoot the crap has an unrelated meaning—to talk casually about unimportant matters. We can find no examples of crap shoot or crapshoot used as a noun for a session of shooting the crap, but we like to think they’re out there somewhere.
In the great crapshoot of life, it is generally agreed there are three things we can’t control: death, taxes and the weather. [CBC]
Talladega is a crap shoot, so you never know what’s going to happen. [USA Today]
[G]lissading can be fun and injury free. Without the tools and the knowledge, though, it’s a crap shoot. [Alaska Dispatch]
Everybody knows that an election with a small turnout can be a crapshoot. [Houston Chronicle]
Profitable trades tend to stay profitable, while untried speculations are always more of a crapshoot. [Smart Money]