Green’s Dictionary of Slang

a large, heavy or clumsy person, an ungainly or stupid lout; a fool.

1838		W. Holloway Dict. of Provincialisms 105/1: Lummox [...] A fat unwieldy person and very stupid into the bargain.
1843		E. Sargent What’s To be Done 22: Don’t I know how that lummocks, Sam Stuggs, makes his money, and ain’t I as good as he.
1841		Sun. Flash (NY) 12 Sept. n.p.: A rather [...] silly fellow, whom his companions were in the habit of calling ‘Lummux Frank’.
1842		Whip & Satirist of NY & Brooklyn (NY) 14 May n.p.: Not forgetting a fat lumix who appeared to be a stranger.
[1843		T. Haliburton Sam Slick in England I 135: You are a disgrace to our great nation, you great lummokin coward, you].
1854		‘Dow, Jr.’ Patent Sermons IV. 149: Man in his original state is little more than a big lummux of a baby.
1858		‘Sweet Betsey from Pike’ in Lingenfelter et al. Songs of the Amer. West (1968) 43: Good bye, you big lummox.
1867		G.W.H. Griffin Hamlet the Dainty Act III: ham.: Another hit, Laertes, in the stomach (Laertes down) laer.: Then it’s below the belt, you great big lummox.
1889		‘Mark Twain’ A Connecticut Yankee 382: As a rule, a knight is a lummux, and sometimes even a labrick.
1889		Dead Bird (Sydney) 21 Sept. 2/2: Frog (to elephant): ‘How far can you jump, you big lummix?’.
1900		T.J. Hains Mr Trunnell Mate of the Ship ‘Pirate’ Ch. xvii n.p.: ‘Jokin’, you lummax!’.
1901		Warren Sheaf (Marshall Co., MN) 31 Oct. 4/2: I knew I was a lunkhead an’ a lummux an’ a gump.
1905		Minn. Jrnl (MN) 22 Oct. 4/1: The young one jiu jitsued a certain ‘big lummix’.
1908		P. MacKaye Poems and Plays 70: As for you, ye lummocks, You need be proud as water in a ditch.
1908		J. Kelley Thirteen Years in Oregon Penitentiary 15: I saw the big lumixer.
1912		R.W. Brown ‘Word-List From Western Indiana’ in DN III:viii 582: lommix or lummix, n. A very careless, awkward person. ‘Watch the big lommix fall; he can’t skate.’.
1914		Ade ‘The New Fable of The Toilsome Ascent’ in Ade’s Fables 172: At school he was a Dummy in Mathematics and a Lummux when it came to Spelling.
1914		Harvard Monthly LIX-LX 150: Come here, you great lummocks.
1916		J. Lait ‘Charlie the Wolf’ in Beef, Iron and Wine (1917) 64: Back goes the big lummox to get a new number.
1922		Vivia Hemphill Down the Mother Lode 27: Hey, you [...] you goot-for-not’ing bucksin lummix, you com mit!
1922		H.G. Dwight Stamboul Nights 37: [...] instead of watching a lot of lazy lummocks dig a hole in the ground.
1927		(con. 1920s) S. Lewis Elmer Gantry 470: What of it, you big lummox!
1931		(con. 1900) Lynn Riggs Green Grow the Lilacs I iii: Don’t set there, you lummy, answer when you’re spoke to!
1934		H. Roth Call It Sleep (1977) 48: Yuh stoopid lummox. Put it way.
1934		A. Ransome Coot Club (1990) 231: He’ll ferget the salt else, the gormless old lummocks!
1940		C. Stead Man Who Loved Children (2001) 251: ‘You lummocks, you dumbbell,’ said Jo, wiping her eyes. ‘Nary a lummocks,’ said Sam, ‘nary a lummocks!’.
1947		B. Schulberg Harder They Fall (1971) 149: A big muscle-bound lummox of a weightlifter.
1959		E. De Roo Go, Man, Go! 80: Filled up on sweets. If you ain’t the lummox.
a.1969		‘Sweet Betsy From Pike’ in G. Logsdon Whorehouse Bells Were Ringing (1995) 217: Betsey, well pleased, cried out with a shout, / ‘You great big lummox, I’m glad you backed out!’.
1976		J. Heller Good As Gold (1979) 355: Every Montik and Donershtik the scampering lummox was in the papers again.
1983		(con. 1940s) D. Nobbs Second From Last in the Sack Race 24: Tha should have had more sense, tha great lummock.
1989		H. Rawson Dict. of Invective (1991) 242: lummox. A big, clumsy person; often a stupid one as well.
1996		H. Roth From Bondage 373: Yeah, he was a lummox all right, that he should have to ask her such a dumb question.
2003		George Hampton & Mike Moore Peter In Wonderland 🌐 He’s gonna go all decky with the whippersnapper. Cork his deadlights. Cut his painter. Board him in the smoke. Coil up his cables, give him the deep six, walk him up ladder lane and down hamp street. He’s gonna kill him, you stupid lummox!
2003		K. Spratley Provincial Eye 53: Oh dear, I am being attacked by a big lummocks with a knife.
2012		C. Stella Rough Riders 35: No, you lummox, like a former gold shield detective knows how to catch the bad guys.