Emily Dickinson Lexicon

COIF, n. [Fr. coiffe; Arm, coeff; It. cuffia, a cap; Sp. cofia, a net of silk or thread worn on the head; Port. coifa, a caul.]

A kind of caul, or cap, worn on the head by sergeants at law and others. Its chief use was to cover the clerical tonsure. – Encyc.