firkin

noun3

1. •
   A small wooden vessel or cask of indeterminate size, used for butter, lard, etc.
2. •
   (UK) A varying measure of capacity, usually being a quarter of a barrel; specifically, a measure equal to nine imperial gallons.

   • 23 Hen. VIII, cap. 4... The barrel of beer is to hold 36 gallons, the kilderkin 18 gallons the firkin 9. But the barrel, kilderkin, and firkin of ale are to contain 32, 16, and 8 gallons. — 1882
3. •
   A measurement for the mass of butter, equalling 56 pounds.