Source : Webster's Revised Unabridged Dictionary (1913)

Wishing \Wish"ing\,
   a. & n. from {Wish}, v. t.

   {Wishing bone}. See {Wishbone}.

   {Wishing cap}, a cap fabled to give one whatever he wishes
      for when wearing it.

Source : WordNet®

wishing cap
     n : a magical cap that secures whatever one wishes for