cord

\ \ [13] Cord ‘string’ and chord ‘straight line’ were originally the same word. They go back to Greek khordé ‘string’, which came into English via Latin chorda and Old French corde. In English it was originally written cord, a spelling which included the sense ‘string of a musical instrument’. But in the 16th century the spelling of this latter sense was remodelled to chord, on the basis of Latin chorda, and it has been retained for its semantic descendants ‘straight line joining two points on a curve’ and ‘straight line joining the front and rear edges of a wing’. (Chord ‘combination of musical notes’ [15] is no relation: it is a reduced version of accord, which comes via Old French acorder from Vulgar Latin *accordāre, a compound verb based on Latin cors ‘heart’, and ironically was originally spelled cord.) Related words include cordon [16], from the French diminutive form cordon, and cordite [19], so named from its often being shaped into cords resembling brown twine.

\ \ Cf.⇒ CHORD, CORDITE, CORDON, YARN