Green’s Dictionary of Slang

(UK Und.) a member of the watch, an officer of the law.

1753		J. Poulter Discoveries (1774) 42: A Horney, a Scout; a Constable, a Watchman.
1789		G. Parker Life’s Painter 136: Aye, do, why should you be dubber-mum’d? there’s no hornies, traps, scouts, nor beak-runners amongst them.
1799		‘Cant Lang. of Thieves’ Monthly Mag. 7 Jan. n.p.: Horney, A A Constable.
1809		G. Andrewes Dict. Sl. and Cant n.p.: Hornees watchmen, constables, or peace-officers.
1812		Vaux Vocab. of the Flash Lang.
1821		D. Haggart Autobiog. 51: The woman missing it immediately, she sent for the hornies.
1832		Egan Bk of Sports 189: ‘We have a warrant,’ answered one of the Horneys.
1848		Flash Dict. in Sinks of London Laid Open.
1859		Matsell Vocabulum 43: horness [sic] Watchmen.
1942		(con. 1890s) S. O’Casey Pictures in the Hallway 6: They hooked it off to get outa reach of the horney’s hand.
1986		T. Ó Canainn Home to Derry in Derry Anthol. (2002) 366: He couldn’t help feeling a certain elation that a dock ‘horney’ had mistaken them for officers .