Kilderkin n. : A small barrel; an old liquid measure containing eighteen English beer gallons, or nearly twenty-two gallons, United States measure.

Example:
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Taxonomy
kilderkin, barrel, imperial gallons, firkins, casks, free encyclopedia, 3⁄4, old English, English unit, search, unit of volume, Dutch, historically, conversions, hogsheads, cubic feet, English, tuns.

Defination from the web:
kilderkin is an old English unit of volume equal to half a barrel or two firkins. It was used as standard size for brewery casks. The word kilderkin comes from Dutch for a small cask. The kilderkin has historically been in the general range of 16 to 18 gallons. ...