ton (n.1)

"measure of weight," late 14c. The quantity necessary to fill a tun or cask of wine, thus identical to tun (q.v.). The spelling difference became firmly established 18c. Ton of bricks in the colloquial figurative sense of what you come down on someone like is from 1884.

ton (n.2)

"prevailing mode, style, fashionable ways," 1769, from French ton (see tone (n.)).

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Definitions of ton from WordNet

ton (n.)
a United States unit of weight equivalent to 2000 pounds;
Synonyms: short ton / net ton
ton (n.)
a British unit of weight equivalent to 2240 pounds;
Synonyms: long ton / gross ton