defatigable (adj.)

"liable to be wearied," 1650s, from defatigate (v.), 1550s, from Latin defatigatus, past participle of defatigare "to weary, tire out, exhaust with labor," from de "utterly, down, away" (see de-) + fatigare "to weary" (see fatigue (n.)). Also see indefatigable.