Word Origin & History
idleO.E. idel "empty, void, useless," common W.Gmc. (cf. O.S. idal, O.Fris. idel "empty, worthless," O.Du. idil, Ger. eitel "vain, useless, mere, pure"), of unknown origin. Idle threats preserves original sense; meaning "lazy" is c.1300. The verb sense of "running slowly and steadily without transmitting
power" (as a motor) first recorded 1916.