1rare Of a person: that has not been asked or called upon (to do something); unbidden.
2Originally: (of a thing, especially an action) unasked for, unsought; not demanded or called for. Later also: not obligatory or compulsory.
3Not needed, not requisite; unnecessary; superfluous.
Late Middle English; earliest use found in John Lydgate (c1370–c1449), poet and prior of Hatfield Regis. From un- + require + -ed.