early 14c., lumpe, "small mass of material, solid but of irregular shape" (1224 as surname), etymology and original sense unknown. Perhaps it was in Old English, but it is not recorded there. Perhaps from a Scandinavian or continental source: Compare Danish lumpe "block, stump, log" (16c.), Middle High German lumpe, early modern Dutch lompe. All appear in the Middle Ages; there seems to be no trace of the word in older Germanic languages.
Late 15c. as "protuberant part;" from 1520s as "a great quantity;" 1590s as "dull, stupid person." Phrase lump in (one's) throat "swelling in the throat," especially "feeling of tightness brought on by emotion," is from 1803. Lumps "hard knocks, a beating" is colloquial, from 1934. Lump sum, covering a number of items at one time, is from 1867 (the same sense of lump is in lump-work, 1851).