FIRKIN, noun fur'kin. A measure of capacity, being the fourth part of a barrel. It is nine gallons of beer, or eight gallons of ale, soap or herrings. In America, the firkin is rarely used, except for butter or lard, and signifies a small vessel or cask of indeterminate size, or of different sizes, regulated by the statutes of the different states.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI