The victim of a confidence game is often called the mark, or the vic. This is an underground slang term that evolved amongst swindlers because the intended victim was said to be "marked" for the sting.

In some instances the mark would literally be marked. This is usually done by traveling crooked carnival game mobs, who were known to hit towns, set up an amusement park and leave after a few days. In this case all the operators of the crooked games of chance would be part of the same mob. When one of the operators was done working a mark he would give him a friendly tap on the shoulder and wish him better luck next time. During this friendly gesture the operator would leave a dusty chalk mark, or a sticker, that all the operators of other games would recognize to mean that this mark has particularly good potential.