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).
early 15c., "to curl up in a ball, to gather into a lump" (implied in lumped), from lump (n.). Transitive meaning "to put together in one mass or group" is from 1620s. Related: Lumped; lumping (from 1705 as a slang present-participle adjective meaning "great, big"):
LUMPING. Great. A lumping pennyworth; a great quantity for the money, a bargain. He has got a lumping pennyworth; frequently said of a man who marries a fat woman. [Grose, "Classical Dictionary of the Vulgar Tongue," 3rd edition, 1796]
"endure" (now usually in antithesis to like), 1791, apparently an extended sense from an older meaning "to look sulky, dislike" (1570s), of unknown origin, perhaps, as OED suggests "of symbolic sound" (compare grump, harumph, glum, etc.). Or from lump (n.) on the notion of "swallow the whole."