mumm, v. i. [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."