Green’s Dictionary of Slang

kiss up (to) v.

to toady to.

1967–8		Baker et al. CUSS 148: Kiss up to Curry favor with a professor.
1989		P. Munro Sl. U.
1997		Da Bomb Summer Supplement 9: Kiss up (v.) To conforming for personal gain (milder form of suck butt).
1997		T. Lindberg Philanthropy mag., I:2 🌐 Brilliantly, Hitt has chosen not to kiss up to Gates.
2000		F. Kellerman Stalker (2001) 557: Tropper must have thought she was kissing up to him.