Origin

The drink was invented and named by fictional secret agent James Bond in the 1953 novel Casino Royale.
"A dry martini," [Bond] said. "One. In a deep champagne goblet."
"Oui, monsieur."
"Just a moment. Three measures of Gordon's, one of vodka, half a measure of Kina Lillet. Shake it very well until it's ice-cold, then add a large thin slice of lemon peel. Got it?"
"Certainly, monsieur." The barman seemed pleased with the idea.
"Gosh, that's certainly a drink," said Leiter.
Bond laughed. "When I'm...er...concentrating," he explained, "I never have more than one drink before dinner. But I do like that one to be large and very strong and very cold and very well-made. I hate small portions of anything, particularly when they taste bad. This drink's my own invention. I'm going to patent it when I can think of a good name."

—Ian Fleming, Casino Royale