In 1849, the New York Herald reported on the arrest of a gentleman by the name of William Thompson.
I use the term ‘gentleman’ here broadly. As the Herald reported:
For the last few months a man has been traveling about the city…he would go up to a perfect stranger in the street, and being a man of genteel appearance, would easily command an interview. Upon this interview he would say after some little conversation, “have you confidence in me to trust me with your watch until to-morrow;” the stranger at this novel request, supposing him to be some old acquaintance not at that moment recollected, allows him to take the watch, thus placing “confidence” in the honesty of the stranger, who walks off laughing and the other supposing it to be a joke allows him so to do. In this way many have been duped…
To those who had heard of these strange interactions, Thompson was known as the “Confidence Man.”
He was, in fact, the first “confidence man” – a term which has sense been colloquially shortened to “con man.”