Forever, endlessly. This hyperbole, like not a hope in hell, dates from the early twentieth century, first appearing in print about 1919. F. Scott Fitzgerald reportedly liked ending a letter with, “Yours till hell freezes over,” and A. A. Fair used it in Stop at the Red Light (1962): “They’ll investigate until hell freezes over.” During the Cuban missile crisis of 1962, U.S. ambassador to the United Nations, Adlai Stevenson, asked the Soviet ambassador if his country had placed missiles in Cuba and said, “. . . I am prepared to wait for my answer until hell freezes over” (Oct. 25, 1962). The negative version, not till hell freezes over, means, of course, “never.”