What is the origin of the idiom "blow smoke" and when to use it?

The idiom "blow smoke" originated from the literal act of blowing smoke into someone's face to deceive or confuse them. This practice, often associated with stage magicians, created an illusion or diversion that allowed the performer to execute a trick or escape unnoticed. Over time, the expression evolved into a metaphorical sense. It is now used to refer to the act of making false statements, exaggerations, or empty promises to mislead or confuse others.

What is the origin of the idiom "blow smoke up one's ass" and when to use it?

The idiom "blow smoke up one's ass" has its origin in a historical medical practice dating back to the 18th century. Prior to the development of modern resuscitation techniques, physicians believed that blowing smoke into the rectum of a supposedly deceased person could revive them. This practice was based on the mistaken belief that the warm tobacco smoke would stimulate the body and restore life. Over time, this expression evolved to figuratively mean the act of insincerely flattering or praising someone excessively to gain favor or manipulate them. It implies that the person doing the flattery is being deceitful or disingenuous in their attempts to win the trust or admiration of another.