kilderkin

noun

1. A small barrel.
2. An old English liquid measure, usually being half a barrel; containing 18 English beer gallons, or 83.178 L.

   “1882: 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. — James Edwin Thorold Rogers, A History of Agriculture and Prices in England, Volume 4, p. 205.”

   “Barrels came in firkins, nine gallons; kilderkins, eighteen gallons; halves, twenty-seven gallons; barrels, thirty-six gallons and hogsheads, fifty-four.”