ton (n.1) Look up ton at
"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) Look up ton at
"prevailing mode, style, fashionable ways," 1769, from French ton (see tone (n.)).