Green’s Dictionary of Slang

a country carter or ploughman.

1663		Man in the Moon 5 May 10: A Country Tuskin affirms he met them on the road flying towards Plimouth.
1719		D’Urfey Pills IV 197: Then did you not hear of a Country Trick? / They say that Tuskin's no Dastard; / For when Country Gillians do play with their Dicks, / Then London must Father their Bastards.
1796		Grose Classical Dict. of the Vulgar Tongue.