Green’s Dictionary of Slang

ass-kiss v.

[backform. f. ass-kisser n.]

(orig. US) to toady;hence as n. ass-kiss, sycophancy.

[US]J. Jones From Here to Eternity (1998) 340: He had earned the management of his gambling shed by being in the same company 17 years and ass-kissing his superiors every minute of that time.
[US](con. early 1950s) J. Peacock Valhalla 268: That rank-happy bastard could ass-kiss all he wanted to.
[US]S. Longstreet Flesh Peddlers (1964) 327: Never petty, never ass-kissing or polishing the red apple for anyone.
[UK]Sun. Mirror 21 Aug. 8: We weren’t ass-kissing.
[US]Simon & Burns ‘Stray Rounds’ Wire ser. 2 ep. 9 [TV script] This new Asec, thinks it’s all loyalty and ass-kiss.