Green’s Dictionary of Slang

(W.I.) an African-born black person; so called by the Creoles, who were born in the West Indies.

1774		E. Long Hist. of Jamaica II 410: The Creole Blacks [...] hold the Africans in the utmost contempt, stiling them, ‘salt-water Negroes’, and ‘Guiney birds’.
1821		J.F. Cooper ‘The Spy’ in Novel Newspaper (1842) I 154/2: I’m sure a Guinea nagur loves heat, as much as a souldier loves his drop.