clump (n.) Look up clump at Dictionary.com
1580s, "lump; cluster of trees," from Middle English clompe "a lump" (c.1300), from Dutch klomp "lump, mass," or Middle Low German klumpe "clog, wooden shoe." Old English had clympre "lump, mass of metal."
clump (v.2) Look up clump at Dictionary.com
"walk heavily," 1660s, imitative. Related: Clumped; clumping.
clump (v.1) Look up clump at Dictionary.com
"to heap or gather in clumps" (transitive), 1824, from clump (n.). Related: Clumped; clumping. Intransitive sense "to form a clump or clumps" is recorded from 1896.