Green’s Dictionary of Slang

1. a manual labourer, thus, adj., razorbacked, uncouth.

1903		A. Adams Log of a Cowboy 81: I reckon the girl was all right, but the family were these razor-backed, barnyard savages.
1906		J.W. Carr ‘Words from Northwest Arkansas’ in DN III:iii 153: razor-back, n. [...] 2. A rustic boor. ‘He acts like a sure enough razorback’. 3. An Arkansan. ‘The Jayhawkers breat the Razorbacks by a close shave.’.
1909		Vintna Dly Chieftain (OK) 25 Sept. 1/2: He was flourishing a shot-gun and threatening to kill more ‘Razor-backed Arkansawyers’.
1913–14		Van Loan ‘Scrap Iron’ in Taking the Count 204: The two sons [...] ran wild as razorbacks.
1936		A.E. Duckett ‘Truckin ’round Brooklyn’ in N.Y. Age 21 Nov. 7/1: She seems to be playing him for an old razor-backed sucker.

2. a circus roustabout.

1894		‘Sl. of the Circus Man’ in Boston Daily Globe 17 Dec. 35: The musicians with a circus are known as ‘wind-jammers,’ the canvasmen and other laborers are ‘razorbacks.’.
1909		Youth’s Companion LXXXIII 289/4: The loaders – ‘razor-backs’, in circus language – were putting the great clanking parade wagons on the flat cars [OED].
1921		P. & T. Casey Gay-cat 147: In all thet crowd with a circus, who’s gonna spot three or four safe-crackers wot is woikin’ as razor-backs er ticket-butchers er the like.
1930		‘Dean Stiff’ Milk and Honey Route 212: Razor back – Circus roustabout.
1931		R.E. Howard ‘Circus Fists’ in Fight Stories Dec. 🌐 The first day I was with the show I licked three razor-backs, the lion-tamer and a side-show barker.
1949		N. Algren Man with the Golden Arm 190: A shock-haired razorback with a bright Bull Durham string hanging over his shirt pocket’s edge.
1962		Ragen & Finston World’s Toughest Prison 814: razor back – A roustabout or circus laborer.