Today's OED antedating: "it ain’t over till the fat lady sings"

It ain’t over till the fat lady sings, slang, jocular and folksy gauge of when the result of an activity is determined, usually in sport (no entry): Two passages: first, article jump-headlined "Hayes Scores 35 Points, Spurs 17-0 Bullet Spurt," by Paul Attner, Washington Post, May 8, 1978, p D4, col 4: "But Motta was not about to start celebrating the end of the series. 'It's not over,' he said. 'It's like an opera. It doesn't end until the fat lady starts singing and that hasn't happened in this one yet.'" And second, article headlined "Signing a Free Agent for a Song," by Nina S. Hyde, Washington Post, June 3, 1978, p B1, col 3: "San Antonio sports editor Dan Cook countered with, 'The opera ain't over 'til the fat lady sings.'"