1520s, "a show or performance of mumming," from Old French mommerie, from momer "to mask oneself" (see mummer). Transferred sense of "ridiculous ceremony or ritual" is from 1540s.
Entries linking to mummery
mummer n.
"one who performs in a mumming, actor in a dumb show," early 15c., probably a fusion of Old French momeur "mummer" (from Old French momer "mask oneself," from momon "mask") and Middle English mommen "to mutter, be silent," which is the source of mum (interjection). "[S]pecifically, in England, one of a company of persons who go from house to house at Christmas performing a kind of play, the subject being generally St. George and the Dragon, with sundry whimsical adjuncts" [Century Dictionary].