Kiss someone’s arse/ass
To kiss someone’s arse/ass or to kiss arse/ass is a vulgar, colloquial metaphor to behave in a flattering and obsequious manner, especially towards a superior, in order to gain favour. In Britain ‘lick’ instead of ‘kiss’ is frequently used. Such expressions date in this sense from the early 18th century, however, an early citation for the literal act can be found in Chaucer The Miller’s Tale c.1387, “He kissed her naked arse.” Kiss-ass as an adjective, as in behaving in a ‘kiss-ass’ manner, is an American development from the early 1980s. See also Brown nose.