1630s, "obsolete, out of date;" 1740, "retired on account of old age," from Modern Latin superannuatus, alteration (perhaps by influence of annual) of Medieval Latin superannatus (which meant "more than a year old" and was used of cattle), from Latin super "beyond, over" (see super-) + annus "year" (see annual, adj.). Earlier in same sense was superannate (c.1600), from Medieval Latin superannatus. Compare French suranner.