"put to work at certain duties, compel to work for one's benefit," 1806, from British public school slang fag (n.) "junior student who does certain duties for a senior" (1785), from fag (v.1). Related: Fagdom (1902); faggery "fatiguing labor" (1853).
1690s, from French fatiguer "to tire" (15c.), from fatigue (see fatigue (n.)). Earlier in same sense was fatigate (1530s), from Latin fatigatus, past participle of fatigare. Related: Fatigued; fatiguing; fatigation (c. 1500).