The word "con man" is short for "confidence man." Wikipedia's article on the confidence trick is pretty interesting:
QUOTE: "A confidence trick or confidence game (also known as a bunko, con, flim flam, gaffle, grift, hustle, scam, scheme, swindle or bamboozle) is an attempt to defraud a person or group by gaining their confidence. The victim is known as the mark
Forum:
"Cults," Sects, and "New Religious Movements"