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."
"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.
<a href="https://www.etymonline.com/word/clumperton">Etymology of clumperton by etymonline</a>
Harper, D. (n.d.). Etymology of clumperton. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/clumperton