"consisting of clumps, of the nature of a clump, lumpy," 1820, from clump (n.) + -y (2). Also noted 1881 in an Isle of Wight glossary as a noun meaning "a stupid fellow." Related: Clumpily; clumpiness. Compare clumperton.
1580s, "lump; cluster or small, close group" (especially of shrubs or trees), from Middle English clompe "a lump" (c. 1300), from a Low German source (such as Dutch klomp "lump, mass," or Middle Low German klumpe "clog, wooden shoe"). Old English had clympre "lump, mass of metal."
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy).