pontoon: English has two words pontoon. The earlier, ‘floating structure’ [17], comes via French ponton from Latin pontō ‘bridge made of boats’, a derivative of pōns ‘bridge’. (Pontō, presumably the same word, was also used for a sort of Gaulish boat, and in that sense is the source of English punt.) Pontoon the card game [20] is an alteration of French vingt-et-un ‘twenty-one’ (the perfect score in pontoon being twenty-one) based on the other pontoon. [pontoon etymology, pontoon origin, 英语词源]