"related notes in music," 1590s, ultimately a shortening of accord (or borrowed from a similar development in French) and influenced by Latin chorda "catgut, a string" of a musical instrument (see cord, n.). Spelling with an -h- first recorded c.1600, from confusion with chord (n.2). Originally two notes; of three or more from 18c.

"structure in animals resembling a string," 1540s, alteration of cord, n., by influence of Greek khorde "gut-string, string of a lyre, tripe," from PIE *ghere- "gut, entrail" (see yarn). The geometry sense is from 1550s; meaning "feeling, emotion" first attested 1784.