Brown nose

To brown nose is an even more vulgar form (if that is possible) of kissing someone’s arse/ass. To brown nose is to act in an obsequious manner in order to gain favour, especially from a superior by figuratively kissing or licking arse/ass. Why such behaviour results in a brown nose is best left unsaid. The expression is thought to have originated in US military and student slang during the 1940s. See also Brownie points.