caisson
UK[ˈkeɪ.sən]US[ˈkeɪ.sɑːn]
n
A large watertight chamber, open at the bottom, from which water is kept out by air pressure. It is used for carrying out construction work under water.
n
A large box or chest, especially one used to hold ammunition.
n
A two-wheeled wagon or cart for carrying artillery ammunition.
Etymology
The word 'caisson' entered English in the 18th century from the French word 'caisson', meaning 'large box' or 'ammunition chest'. The French term is itself a derivative of 'caisse', meaning 'box' or 'case', which originates from the Latin 'capsa', denoting a box for holding things. This Latin root, related to 'capere' (to take, to hold), is also the ancestor of English words like 'case' and 'capsule'. The specialized engineering meaning of a watertight chamber developed from the concept of a large, sealed box used for foundational work, particularly in the construction of bridge piers and other underwater structures.
Analysis
The word is a loanword from French and is treated as a single, unsegmentable unit in modern English.
Examples
The workers descended into the caisson to excavate the riverbed for the new bridge pier.
During the Civil War reenactment, the horse-drawn caisson carried cannonballs to the artillery position.
The museum's exhibit featured an antique ammunition caisson from the 19th century.