Blow smoke up someone's arse / ass

To blow smoke up someone's ass/arse means to flatter, deceive, or lie to someone, and is originally American, dating from the 1940s. The core is to 'blow smoke', which means to deceive, as in a smoke screen, and is implied in the expression smoke and mirrors. The fortuitous addition of the phrase, 'up someone's ass/arse', has led to the false claim that the origin is connected to primitive smoke enemas, dating from the 1700s and even earlier, when literally, blowing tobacco smoke up rectums by means of bellows was thought to cure all sorts of ailments.