A machine in which cotton or wool is opened and cleansed by
   the action of long spikes projecting from a drum which revolves within
   a box studded with similar spikes; -- probably so called from having
   been originally a cylindrical cage made of willow rods, though some
   derive the term from winnow, as denoting the winnowing, or cleansing,
   action of the machine. Called also willy, twilly, twilly devil, and
   devil.