To add a little to Jumbuck's response, the earliest use of the word 'rubber' to suggest a deciding game - best of three, five etc - was in the 16th century and in reference to bowls, as stated, rather than cards. Its first use in card-playing - whist, specifically - came nearly 200 years later. The actual origin of the word is obscure, but it appears to have nothing to do with 'rubber' as in 'rubber ball'...never mind condom! If it's any help, the French equivalent is apparently, robre, which has clearly no connection with their caoutchouc.