Blow Smoke .....

[Theland]

What does the saying used in U.S. films mean, and how did it originate?
"Don't blow smoke up my a**."

[Quizmonster]

To blow smoke is to pretend you're more important than you really are or that you know something that you're really not very familiar with. I'm not sure whether adding the "up my" element changes that basic meaning or not!