fir·kin /ˈfɝkən/
  木製小桶,容量名
  Fir·kin n.
  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.]
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  firkin
       n 1: a British unit of capacity equal to 9 imperial gallons
       2: a small wooden keg
  Firkin
     Used only in John 2:6; the Attic amphora, equivalent to the
     Hebrew bath (q.v.), a measure for liquids containing about 8 7/8
     gallons.