Webster’s Revised Unabridged Dictionary · 1913
Firkin
Fir′kin (fẽr′kĭn), n. [From AS. feówer four (or an allied word, perh. Dutch or Danish) + -kin. See Four.] 1. A varying measure of capacity, usually being the fourth part of a barrel; specifically, a measure equal to nine imperial gallons. [Eng.]
2. A small wooden vessel or cask of indeterminate size, — used for butter, lard, etc. [U.S.]