"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" (cognates: Flemish klammig, Low German klamig "sticky, damp," Old English clæman "to smear, plaster;" cognates: clay). With -y(2). Related: Clammily; clamminess.