Green’s Dictionary of Slang

gin, or any other strong liquor.

1725		New Canting Dict. n.p.: south-sea a strong distill’d Liquor, so called by the Inhabitants and Clients of Newgate, &c.
1728		T. Walker The Quaker’s Opera I i: qu.: What hast thou got? poor.: Sir, you may have what you please, Wind or right Nantz or South-Sea, or Cock-my-Cap, or Kill-Grief, or Comfort, or White-Tape.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. 1725].
1785		Grose Classical Dict. of the Vulgar Tongue.
a.1790		H.T. Potter New Dict. Cant (1795).
1809		G. Andrewes Dict. Sl. and Cant.
1821		Flash Dict.
1835		G. Kent Modern Flash Dict.
1848		Flash Dict. in Sinks of London Laid Open.
c.1850		Duncombe New and Improved Flash Dict. n.p.: South-sea sherry Geneva.
1858		A. Mayhew Paved with Gold 256: She’s a rum ’un, and as fond of ‘a line of the old author’ (brandy) or a drop of the ‘South Sea Mountain’ (gin) as any ‘doxy’ (woman) in Stafford.