The Collaborative International Dictionary of English v.0.48:

Warlock \War"lock\, n. [OE. warloghe a deceiver, a name or the
   Devil, AS. w?rloga a belier or breaker of his agreement,
   word, or pledge; w?r covenant, troth (aki? to L. verus true;
   see Very) + loga a liar (in comp.), le['o]gan to lie. See
   3d Lie.]
   A male witch; a wizard; a sprite; an imp. [Written also
   warluck.] --Dryden.
   [1913 Webster]

         It was Eyvind Kallda's crew
         Of warlocks blue,
         With their caps of darkness hooded!      --Longfellow.
   [1913 Webster]