Ok, I picked this up at
http://www.pokerroomgold.co.uk : "The game of poker began in the middle 1800's in bars, saloons and on riverboats in the mid-west and western United States. The word "poker" was derived from the French game, "Poque" and the British game, "Brag." Coins, gold dust and gold nuggets were used as the monetary units in early poker games. Soon thereafter, chips replaced coins and gold particles, as they were easier to manage. Chips were made from ivory, bone, wood, paper and a composition made from clay and shellac".