relaxation (n.)

late 14c., relaxacioun, "a rupture, a hernia" (a sense now obsolete); mid-15c., "remission of a burden or penalty," from Old French relaxacion (14c.) and directly from Latin relaxationem (nominative relaxatio) "an easing, mitigation, relaxation," noun of action from past-participle stem of relaxare "loosen, open, stretch out" (see relax).

Meaning "relief from hard work or ordinary cares; a state or occupation intended to give mental or bodily relief after effort or ordinary occupations and cares" is from 1540s. Sense of "remission or abatement of rigor or intensity" is from 1690s.