Green’s Dictionary of Slang

dunaker n.

also donaker, donnaker, dunneker
[dunnock n.]

a cow-stealer.

Wandring whores complaint n.p.: The ninteenth [sic] a Donnaker that will make vows / To go in the Country and steal all the Cows.
[UK]Nicker Nicked in Harleian Misc. II (1809) 108: There come in shoals of hectors, trepanners, [...] bulkers, droppers, gamblers, donnakers, cross-biters.
[UK]‘L.B.’ New Academy of Complements 205: The seventeenth a Dun-aker, that will make vows, / To go to the Countrey and steal all the Cows.
[UK]Poor Robin [as cit 1669].
[UK]B.E. Dict. Canting Crew.
[UK]‘Black Procession’ in Farmer Musa Pedestris (1896) 39: The seventeenth a dunaker, that stoutly makes vows, / To go in the country and steal all the cows.
[UK]New Canting Dict. n.p.: dunaker a Stealer of Cows, or Calves, &c. The Forty-third Order of Villains.
[UK]Bailey Universal Etym. Eng. Dict. [as cit. 1725].
[UK]Grose Classical Dict. of the Vulgar Tongue.
[UK]Lex. Balatronicum.
[US]Matsell Vocabulum.
[UK]Hotten Dict. of Modern Sl. etc.
[UK]Hotten Sl. Dict.
[Aus]Crowe Aus. Sl. Dict. 26: Dunneker, a cattle-thief.