The phrase “slipping a Mickey” likely originated with Mickey Finn, a Chicago saloon owner known for drugging and robbing customers. Finn owned a bar called the Lone Star Saloon and Palm Garden in 1896, where he partook in a few less than stellar activities, one of which was selling stolen items.
Finn somehow obtained some white powder, which was believed to be chloral hydrate, and concocted two drinks with the stuff. One was mixed with beer, and the other was mixed with alcohol and other substances. When the patron got a taste of the drink, they would be knocked out. Finn’s associates would take them to a back room while they were incapacitated and steal their possessions while they were dozing. The person would then be dropped in an alley without their belongings and unable to remember what happened when they awoke.
After paying off the Chicago P.D. for a time, Finn’s bar was eventually shut down in 1903. He had sold the recipe for the concoction to other bar owners by then, and the term “Mickey Finn,” or “slipping a Mickey,” became synonymous with a drink that put someone out on the floor.
Finn was later arrested in 1918 for running an illegal bar in South Chicago. During the same year, over 100 waiters, along with four sellers of what was called “Mickey Finn powder,” were arrested for the widespread practice of poisoning patrons around Chicago. The powder was found to be antimony potassium tartrate, which was also known as “emetic tartar.” The substance was lethal in large quantities and induced dizziness, vomiting, and headaches.
Here’s a modern example of “slipping a Mickey.”