Green’s Dictionary of Slang

(Aus.) a cattle thief.

1877		Queenslander (Brisbane) 10 Mar. 21/1: The sun-downer, the house-polanter, the brand faker, and the duffer, the cattle killer, the cattle thief and the sheep-stealer would disquiet us.
1879		Star (Canterbury) 15 Sept. 2/7: It does not become a cattle duffer to talk in that manner.
1886		Melbourne Punch 15 July n.p.: Cattle duffers on a jury may be honest men enough, / But they’re bound to visit lightly sins in those who cattle duff.
1888		‘Rolf Boldrewood’ Robbery Under Arms (1922) 32: No cattle-duffer in the colonies could have had a better pair of mates than old Sally and Crib.
1893		K. Mackay Out Back 108: What’s that, you blarsted cattle duffer?
1901		Bulletin (Sydney) 7 Sept. 14/1: A noted cattle-duffer has just been laid by the heels in a Far-Western town, the luck that has kept him out of gaol for a lifetime having deserted him at a critical moment.
1903		Star (Canterbury) 28 Feb. 4/2: He has displayed qualities that would have made him a successful cattle-duffer or bushranger.
1908		G. Seagram Bushmen All 33: A notorious gang of Queensland cattle duffers .
1912		Truth (Wellington) 26 Oct. 7/6: [pic. caption] Cuthbert William Bridge (Railway Porter and Cattle Duffer).
1926		in J. Doone Timely Tips For New Australians.
1926		M. Forrest Hibiscus Heart 228: The police had a brush with the cattle-duffers.
1932		‘William Hatfield’ Ginger Murdoch 237: Cattle-duffers, wanted for gettin’ down on Ferber’s stock.
1965		R.H. Conquest Horses in Kitchen 213: Tell me, what the devil would cattle-duffers do with drilling gear?