late 15c., "laborious attempt, strenuous exertion," from French effort, from Old French esforz "force, impetuosity, strength, power," verbal noun from esforcier "force out, exert oneself," from Vulgar Latin *exfortiare "to show strength" (source of Italian sforza), from Latin ex "out" (see ex-) + Latin fortis "strong" (see fort).
Effort is only effort when it begins to hurt. [José Ortega y Gasset, writing of Goethe in Partisan Review, vol. xvi, part ii, 1949]
Related: Efforts "voluntary exertion," also "result of exertion."