1916, "one who acts as a decoy for a gambler, auctioneer, etc." (probably originally circus or carnival argot), probably a shortened form of shillaber (1913) with the same meaning, origin unknown. The verb is attested from 1914.
n. someone planted in the crowd to urge others to buy something, participate in something, etc. : The guy's a shill! Don't fall for this setup!
in. to advertise for something; to give a sales pitch for something. : Four stars of an old television show were there shilling for a major computer firm.
Dictionary of American Slang and Colloquial Expressions by Richard A. Spears.Fourth Edition. Copyright 2007. Published by McGraw Hill.
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