What is the X in X-mas?
1800, from mummy + -fication.
1620s, from French momifier, from momie "mummy," from Medieval Latin mumia (see mummy) + -fier "to make into" (see -fy). Related: Mummified; mummifying.
mummification mum·mi·fi·ca·tion (mŭm'ə-fĭ-kā'shən)n. The shrivelling of a dead and retained fetus.