Green’s Dictionary of Slang

a worker who refuses to accept anything but full, union-negotiated wages.

1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: Flints, journeymen taylors, who on a late occasion, refused to work for the wages settled by law. Those who submitted, were by the mutineers stiles dungs, i.e. dunghills.
1791		‘Brother Rook’ Willy Wood & Greedy Grizzle 10: Well might the edge of Grizzle’s tongue / Have shap’d a flint into a dung.
1805		‘Jeremy Swell, Gent.’ Tailors’ Revolt 18: There are no sneaking dungs or milksops here; / No, they’re such flints as gen’rals might desire, / Heroic flints, aye flints too full of fire.
1811		Lex. Balatronicum.
1825		Pierce Egan’s Life in London 9 Jan. 398/2: These two tailors — flints to the backbone — [...] demanded grog.
1837		N.Y. Times 1 Mar. 2/6: The war waged by the flints against the dungs, or in other words the strike of the Taylors.
1838		‘Alfred Crowquill’ Seymour’s Humourous Sketches (1866) 167: napps [...] as dun his dooty like a rig’lar flint.
1859, 1860		Hotten Dict. of Modern Sl. etc.
1863		Story of a Lancashire Thief 12: I never even heard him talk workmen’s slang; he’d never speak about flints and dungs, or fat, or elbow grease.
1873		Sl. Dict.