Wine.
A magnum of wine is two quarts; a tappit-hen of wine or rum is a double magnum; a jeroboam of wine or rum is a double “tappit-hen”; and a rehoboam (q.v.) is a double jeroboam.
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Entry taken from Dictionary of Phrase and Fable, edited by the Rev. E. Cobham Brewer, LL.D. and revised in 1895.