Source : Webster's Revised Unabridged Dictionary (1913)

Mumm \Mumm\, v. i. [imp. & p. p. {Mummed}; p. pr. & vb. n.
   {Mumming}.] [D. mimmen to mask, mom a mask; akin to G. mumme
   disguise; prob. of imitative origin, and akin to E. mum,
   mumble, in allusion to the indistinctness of speech
   occasioned by talking from behind a mask. Cf. {Mumble},
   {Mummery}.]
   To sport or make diversion in a mask or disguise; to mask.

         With mumming and with masking all around. --Spenser.