Shill

A shill is a confidence trickster's accomplice who pretends to be an enthusiastic customer in order to encourage the victim, or mark. ("I can walk!", or "I can see!", or "I'll buy ten!"), and in the case of a form of betting that requires skill, the trickster and shill play out one or more times that the shill wins and create the impression that it is easy to win. The technique employs group dynamics as an element of crowd psychology: the victim comes to feel that s/he stands in good company, does not lag in social sharpness, and should not delay in latching onto a good thing. One could regard groupies as a sub-class of the class of shills.

In the broader marketing arena, a shill functions as a provider of a testimonial - apparently unsolicited. In sales, the customer reference or the reference site equates to the shill.

The term is also used by illusionistss to describe a collaborator in a magic trick.

The word is probably an abbreviation of shillaber, which has the same meaning, and appeared early in the 20th century from an unknown origin.