Source : Webster's Revised Unabridged Dictionary (1913)

Warming \Warm"ing\,
   a. & n. from {Warm}, v.

   {Warming pan}, a long-handled covered pan into which live
      coals are put, -- used for warming beds. --Shak.

Source : WordNet®

warming pan
     n : a long-handled covered pan holding live coals to warm a bed