from
The Collaborative International Dictionary of English v.0.48
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.
[1913 Webster]
With mumming and with masking all around. --Spenser.
[1913 Webster]