Green’s Dictionary of Slang

(US) pleasure; sexual advances, seduction; also as adv., happily, cheerfully.

1903		E.W. Townsend Sure 17: [The] shuffer tries gaily- gaily wit Duchess, and I was willing for him to have a nice easy job like dat.
1903		E.W. Townsend Sure 60: De Roseleafers is a good lot of boys and goils, but deir notion of gaily-gaily always takes in a scrap.
1903		E.W. Townsend Sure 107: We was soon gassing gaily-gaily.