[prob. immediately a. Du. bak trough, tub, a. F. bac ‘ferry boat, punt’ (see BAC), also ‘trough, basin, mash-tub,’ in med.L. bacus, baccus, ferry boat (11th c. in Du Cange): cf. also late L. bacca ‘vas aquarium,’ Isidore; remoter origin uncertain.] A large shallow vessel (chiefly for liquids); a tub, trough, vat, cistern; esp. applied to those used by brewers, dyers and picklers.
1682. Lond. Gaz., No. 1684/4. To be Sold, six Backs, several Stills and Worms.
1737. Miller, Gard. Dict., s.v. Anil, Backs or Vats of Stone-work, well cemented.
1791. Hamilton, Berthollet’s Dyeing, I. I. II. ii. 159. Long copper or wooden vessels, called troughs or backs.
1794. G. Adams, Nat. & Exp. Phil., I. xi. 483. The gaseous atmosphere of a back of beer in fermentation.
1811. Mem. R. Cecil, Introd. 8. His father had in this ground several large backs of water.
1818. Scott, Rob Roy (1818), III. 13 (Jam.). Narrowly escaping breaking my shins over a turf back and a salting tub.
