early 12c., "come into agreement," also "agree, be in harmony," from Old French acorder "agree, be in harmony" (12c.), from Vulgar Latin *accordare "make agree," literally "be of one heart, bring heart to heart," from Latin ad "to" (see ad-) + cor (genitive cordis) "heart" (used figuratively for "soul, mind"), from PIE root *kerd- "heart." Compare concord, discord. Related: Accorded; according.
late 13c., "agreement, harmony of opinions," accourd, acord, from Old French acorde, acort "agreement, alliance," a back-formation from acorder "reconcile, agree, be in harmony" (see accord (v.)). Meaning "will, voluntary impulse or act" (as in of one's own accord) is from mid-15c.