"The phrase dates back to 1904, and comes from the blue chips used as the highest denomination chips in poker games. Poker, as in gambling, as in bet your money and lose your shirt. "Blue chip" stocks today may be the most stable and valuable stocks, but the folks who started using the expression on the Stock Exchange evidently were well aware that the similarities between their enterprise and a high-stakes poker game ran deep."

Don't quote me, as this was cut and pasted from a Metacrawler web search for "origins of blue chip stocks" http://www.metacrawler.com which sometimes produces more specific responses than Google, which uses links and some different criteria for hits.