A lumper was a man who did the work of carrying things into a ship, or out of it.
"Monsoon, you son of a lumper potato," cried out a surly, gruff voice from a berth opposite.
So a lumper, or 'longshoreman, had told the men where to put things.
lumper, a low thief who haunts wharves and docks, and robs vessels, also a person who sells old goods as new.
early 14c., lumpe (1224 as surname), probably in Old English, perhaps from a Scandinavian source (cf. cognate Danish lumpe, 16c.), of unknown origin. Cf. also Middle High German lumpe, early modern Dutch lompe. Phrase lump in (one's) throat "feeling of tightness brought on by emotion" is from 1803. Lumps "hard knocks, a beating" is colloquial, from 1934. Lump sum, one covering a number of items, is from 1867.
early 15c., "to curl up in a ball, to gather into a lump" (implied in lumped), from lump (n.). Meaning "to put together in one mass or group" is from 1620s. Related: Lumped; lumping.
"endure" (now usually in contrast to like), 1791, apparently an extended sense from an older meaning "to look sulky, dislike" (1570s), of unknown origin, perhaps a symbolic sound (cf. grump, harumph, etc.). Related: Lumped; lumping.
LUMPING. Great. A lumping pennyworth; a great qualtity for the money, a bargain. He has got a lumping pennyworth; frequently said of a man who marries a fat woman. ["Dictionary of Buckish Slang, University Wit, and Pickpocket Eloquence," London, 1811]
A person who loads and unloads trucks: ''Lumpers'' unload the trailer for him
[1940s+ Truckers; found by 1796 as ''those who load and unload ships'']