Green’s Dictionary of Slang

kiss someone’s arse v.

also kiss someone’s ass, ...assets, ...behind, ...breech, ...brown end, ...bum, ...butt, ...rump, ...tail
[arse n./ass n./bum n.1 (1)/butt n.1 (1a)/tail n. (1)]

[mid-17C+] to fawn, to act the sycophant, to toady to someone.