Source : Webster's Revised Unabridged Dictionary (1913)

Whetstone \Whet"stone`\, n. [AS. hwetst[=a]n.]
   A piece of stone, natural or artificial, used for whetting,
   or sharpening, edge tools.

         The dullness of the fools is the whetstone of the wits.
                                                  --Shak.

         Diligence is to the understanding as the whetstone to
         the razor.                               --South.

   Note: Some whetstones are used dry, others are moistened with
         water, or lubricated with oil.

   {To give the whetstone}, to give a premium for extravagance
      in falsehood. [Obs.]