Mickey or Mickey Finn

A Mickey was erroneously believed to be potion of “knockout drops” designed to render a bar patron unconscious. Actually it is a potion surreptitiously added to a bar patron’s drink to induce diarrhea. A moment’s reflection with prove the point. No bar owner wants an unconscious man on his hands. He does want to render an objectionable patron so uncomfortable that he will depart the premises and, with luck, permanently. In the Dictionary of American Slang, it is noted that the original Mickey Finn was a laxative for horses.