Rubber

Originally American slang for condom that dates from the late 19th century because 19th century condoms were in fact made from rubber (latex condoms were only manufactured from the 1920s). Rubber as in a series of games or contests dates from the 16th century but its origin is unknown. The OED suggests, however, it may derive from the act of rubbing out or erasing the scores before the start of the next game, especially card games. Dead rubber is a contest in a series of games where the overall outcome of the series has already been decided.