The Collaborative International Dictionary of English v.0.48:

Whim \Whim\, n. [Cf. Icel. hwima to wander with the eyes, vim
   giddiness, Norw. kvima to whisk or flutter about, to trifle,
   Dan. vimse to skip, whisk, jump from one thing to another,
   dial. Sw. hvimsa to be unsteady, dizzy, W. chwimio to move
   briskly.]
   [1913 Webster]
   1. A sudden turn or start of the mind; a temporary
      eccentricity; a freak; a fancy; a capricious notion; a
      humor; a caprice.
      [1913 Webster]

            Let every man enjoy his whim.         --Churchill.
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   2. (Mining) A large capstan or vertical drum turned by horse
      power or steam power, for raising ore or water, etc., from
      mines, or for other purposes; -- called also whim gin,
      and whimsey.
      [1913 Webster]

   Whim gin (Mining), a whim. See Whim, 2.

   Whim shaft (Mining), a shaft through which ore, water,
      etc., is raised from a mine by means of a whim.
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   Syn: Freak; caprice; whimsey; fancy.

   Usage: Whim, Freak, Caprice. Freak denotes an
          impulsive, inconsiderate change of mind, as by a child
          or a lunatic. Whim is a mental eccentricity due to
          peculiar processes or habits of thought. Caprice is
          closely allied in meaning to freak, but implies more
          definitely a quality of willfulness or wantonness.
          [1913 Webster]