Don't blow smoke up my ass

Origin

The core of this vulgar idiom, 'blowing smoke,' has roots in the 19th century, referring to the act of creating illusions or obscuring the truth, much like a magician might use smoke and mirrors to deceive. However, the phrase truly gains its sharp, crude edge with the addition of 'up my ass.' This intensely physical and highly offensive addendum transforms a simple warning against deception into a visceral rejection of insincere flattery or outright lies. It conveys a deep contempt for the attempt to force falsehoods or empty praise upon someone, implying that the deception is as invasive and insulting as the literal act. This vivid, no-nonsense expression likely solidified in American English during the mid-20th century, becoming a blunt and unforgettable way to demand honesty and dismiss any form of flattery or pretense.