kiss somebody's arse

Từ điển Oxford Advanced Learner 8th

kiss sb's ˈarse idiom
(BrE) (NAmE kiss sb's ˈass, kiss ˈass) (taboo, slang)to be very nice to sb in order to persuade them to help you or to give you sth  A more polite way to express this is lick sb's boots.
Main entry: ↑kiss_idiom