Caisson

Part of speech: noun

Pronunciation: /ˈkeɪ.sən/

Definitions

1. A watertight chamber used in underwater construction ; a large box or container for storage or transport ; a two-wheeled cart designed to carry artillery ammunition on the battlefield
2. A sealed structure to allow workers to operate underwater ; a substantial container for holding goods or equipment ; a vehicle used by the military to move artillery shells and supplies
3. An enclosed space that provides dry working conditions below water ; a robust box for carrying or storing items ; a specialized carriage for transporting large quantities of artillery ammunition during combat

Etymology: "Caisson" reached English straight from French, where it meant a large box or chest, and the French word traces back through Italian to the Latin "capsa," a box or case. That same ancestry makes it a doublet of "cassone," the Italian word for a large decorated chest, and of "cajón," the Spanish word for a crate or box, so three languages share one family of words for a container. The sense of a watertight chamber for underwater work developed from the basic idea of a box. A caisson is a sealed chamber, open at the bottom, in which workers can dig beneath water or soft ground while compressed air keeps the water out. The military sense, a two-wheeled cart for carrying artillery ammunition, came from the same box meaning, since the vehicle was essentially a chest on wheels.

Synonyms: waterproof chamber, floating container