clump (n.)
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)
"walk heavily," 1660s, imitative. Related: Clumped; clumping.
clump (v.1)
"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.