[a. OF. fust (mod.F. fût) cask, primarily log, tree-trunk:L. fustem cudgel.]
† 1. A cask for wine; in phrase to savour of the foist: to be fusty. Obs.
a. 1533. Ld. Berners, Gold. Bk. M. Aurel. (1546), Q b. Good wyne sometyme sauoureth of the foyst.
2. Hence, Fustiness. [F. fust (Cotgr.).]
1819. Rees, Cycl., Foist, used to signify a musty sort of smell among hay, straw, grain, and other farm products.
1876. Whitby Gloss., Foist, the mildewd scent of a cellar.