- spell (n.2)
- 1620s, "a turn of work in place of another," from spell (v.2); compare Old English gespelia "a substitute." Meaning shifted toward "continuous course of work" (1706), probably via notion of shift work (as at sea) where one man or crew regularly "spelled" another. Hence "continuous stretch" of something (weather, etc.), recorded by 1728. Hence also, via the notion in give a spell (1750) "relieve another by taking a turn of work" came the sense "interval of rest or relaxation" (1845), which took the word to a sense opposite what it had at the start.