As a kid I remember thinking what a terrific coincidence it was that the only horse to beat Man O' War was named Upset. Then I heard that the word "upset" didn't have that particular meaning until AFTER Man O' War's defeat at the hands of Upset. (which was perhaps a Beamonesque effort on the part of Upset).
I wasn't particularly
upset about having my "coincidence" ruined. It also seemed pretty cool that horseracing had changed the English language. Then I read that it WAS a coincidence after all. "upset" was already used before the 1919 race to mean a surprise victory by an underdog.
I just tried to verify this in my 1971 OED, but I couldn't find that definition even listed, which is odd in itself. But I did find a couple of online references to a word researcher named George Thompson who in 2002 found some newspaper uses of upset (as in surprise victory) dating back to the late 19th C.
http://message.snopes.com/showthread.php?t=2435
http://en.wikipedia.org/wiki/Upset
So now I'm back to thinking it was an amazing coincidence.
--Dunbar