Green’s Dictionary of Slang

1. very well.

1899		W.J. Kountz Billy Baxter’s Letters 49: If some guy cuts in on your steady [...] you are going to call her fine and plenty, aren’t you?
1958		(con. 1940s) B. Behan Borstal Boy 345: You know bloody fine what I’m talking about.
1970		G. Scott-Heron Vulture (1996) 8: Smoky [...] asked me how I would like to make some easy money. I said I’d like it fine.
2019		A. Parks February’s Son 87: Who was he kidding? He knew fine well what he was doing.

2. (orig. US black) attractively.

1938

N.Y. Amsterdam News 19 Feb. 17: He doesn’t have to be good looking or dress so fine.