So, in baseball (and, in other sports, I suspect), in a three (or five, or seven) game series that is tied going into the final game, that final game is often called a "rubber game" or just a "rubber". Where does that usage come from? One site I read mentioned that it came into the language in 1599, but couldn't find any consensus about whence it came. Any knowledge/theories/wild-ass guesses here?