- unison
- 1574, from M.Fr. unisson "unison, accord of sound" (16c.), from M.L. unisonus "having one sound, sounding the same," from L.L. unisonius "in immediate sequence in the scale, monotonous," from L. uni- "one" (see one) + sonus "sound" (see sound (n.1)). Sense of "harmonious agreement" is first attested 1650.