Green’s Dictionary of Slang

1. (UK Und.) a criminal beggar who tours the country posing as a gentleman farmer fallen on hard times, backed by suitably impressive, if counterfeit, papers.

1753		J. Poulter Discoveries (1774) 39: Sky-Farmers are People that go about the Country with a false Pass, signed by the Church-Wardens and Overseers of the Parish or Place that they lived in, and some Justice of the Peace, but the Names are all forged [...] they extort Money, under pretence of sustaining Loss by Fire, or the Distemper amongst the horned Cattle.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: Sky Farmers. Cheats who pretend they were farmers in the isle of Sky, or some other remote place, and were ruined by a flood, hurricane, or some such public calamity: or else called sky farmers from their farms being in nubibus, ‘in the clouds.’.
1811		Lex. Balatronicum [as cit. 1785].
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1840		Sthn Reporter (Cork) 13 Oct. 3/4: The system of ruffianism practised by those fellow called [...] sky farmers, is insufferable. They band together to rob and plunder the unwary farmers.

2. (Anglo-Irish) a farmer with very little, if any, land.

1837		Clare Jrnl 9 Nov. 3/3: A sky farmer from the vicinity of St Patrick’s-well, fell into the Long Dock [...] and was drowned.
1879		C.J. Kickham Knocknagow 232: A beggarly sky farmer that’s stuck in the mud from mornin’ to night, an’ don’t know beef from mutton.
1910		P.W. Joyce Eng. As We Speak It In Ireland.