warlock a man who practises witchcraft; a sorcerer. In Old English wǣrloga meant ‘traitor, scoundrel, monster’, and also ‘the Devil’, from wǣr ‘covenant’ + an element related to lēogan ‘belie, deny’. From its application to the Devil, the word was transferred in Middle English to a person in league with the devil, and hence a sorcerer. It was chiefly Scots until given wider currency by Sir Walter Scott.

warlock †traitor, scoundrel; †the Devil; savage or monstrous creature OE.; sorcerer, wizard XIV. OE. wǣrloga (= OS. wārlogo), f. OE. wǣr covenant = OHG. wāra truth, ON. várar pl., solemn promise, vow + *loʒ-, wk. grade of the base of lēoġan LIE2. ME. warlow(e) (repr. OE. wǣrloga) was superseded by the Sc. var. warlo(c)k (XVI).

war·lock / ˈwôrˌläk/ • n. a man who practices witchcraft; a sorcerer.