The word ton or tonne is derived from the Old English tunne, and ultimately from the Old French tonne, and referred originally to a large cask with a capacity of 252 wine gallons, which holds approximately 2100 pounds of water. Such a barrel (of any similar volume) is still called a tun in British English, but this usage is dying out.
The modern spelling tonne, almost always referring to the metric ton of 1000 kilograms (or the associated obsolete force unit) when used in English, is a direct borrowing from the French language.
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Bode - 100 Holy Paladin - Lightbringer