- ton
- late 14c., tonne, unit for measuring the carrying capacity of a ship, originally "space occupied by a tun or cask of wine," thus identical to tun (q.v.). The two words were not differentiated until 1680s. The measure of weight is first recorded late 15c.; the spelling ton is from 1530s, and became firmly established 18c. Tonnage (early 15c.) originally was "tax or duty on wine imported in tuns." Modern tonne (1877) is the Fr. form of the word, adopted for Eng. use to denote a metric ton (1,000 kg.).