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A “tinhorn gambler,” according to several dictionaries, refers to a game of chance operator who pretends to have money, ability or influence.
The phrase is said to come from people who set up chuck-a-luck games with few funds and a cheap metal (versus leather) chute, called a horn — individuals whom faro dealers disparaged as being petty.
Yet, a 1908 Las Vegas Age article explains that “tin horn gambler” describes a player rather than operator, a low roller specifically, and originated in 1888 by Honorable James Orndorff who, while dealing in a gambling house on the Comstock Lode, told a patron betting small amounts, “You’re cheaper than a tin horn.”
I always thought of a tinhorn gambler as a new, clueless kind of gambler.