pontoon

Etymology 1

Borrowed from Middle French ponton, from Old French ponton, from Latin pontō, pontōnem (“ferryboat”), from pōns (“bridge”).

noun

1. A flat-bottomed boat or other floating structure used as a buoyant support for a temporary bridge, dock or landing stage.
2. (by extension) A bridge with floating supports.
3. A box used to raise a sunken vessel.
4. A float of a seaplane.
5. A lighter or barge used for loading or unloading ships.

Etymology 2

Probably from vingt-un, an obsolete variant of vingt-et-un (“twenty-one”), from French.

noun

1. (card games) A card game in which the object is to obtain cards whose value adds up to, or nearly to, 21 but not exceed it.