What is the X in X-mas?
"soft and sticky," late 14c., probably from Middle English clam "viscous, sticky, muddy" (mid-14c.), from Old English clæm "mud, sticky clay," from Proto-Germanic *klaimaz "clay" (cf. Flemish klammig, Low German klamig "sticky, damp," Old English clæman "to smear, plaster;" cf. clay). With -y (2). Related: Clammily; clamminess.