Emily Dickinson Lexicon

CAST'A-NET, n. [Sp. castañeta, castañuela; Port. castanheta; Fr. castagnette; It. castaguetta. This word seems to be from castaña, a chestnut, so named from the resemblance to two chesnuts.]

An instrument composed of small concave shells of ivory or hard wood, shaped like spoons, placed together, fastened to the thumb, and beat with the middle finger. This instrument is used by the Spaniards, Moors and Bohemians, as an accompaniment to their dances, sarabands and guitars. – Span. Dict. Encyc.