“blowing smoke up your ass.”

Tobacco Smoke Enemas (1750s – 1810s)

The tobacco enema was used to infuse tobacco smoke into a patient’s rectum for various medical purposes,

primarily the resuscitation of drowning victims.

A rectal tube inserted into the anus was connected to a fumigator and bellows that forced the smoke towards

the rectum.

The warmth of the smoke was thought to promote respiration.

Doubts about the credibility of tobacco enemas led to the popular phrase “blowing smoke up your ass.”

Amazingly, it is still in constant use in Washington D.C., by the best senators and representatives money can buy.

I do not know about the last claim, but in case you doubt the rest:  http://en.wikipedia.org/wiki/Tobacco_smoke_enema