Wow, thanks, Dr. Bill! I'll bet not too many of us knew this (I quote from the site):
In 1897 Tod Sloan began riding in England. His unusual riding style coupled with his flamboyant personality brought him instant fame. He called himself Todhunter and English race-goers called him Toddy. But it was George M. Cohan who coined Sloan's most famous nickname, Yankee Doodle Dandy, written about the American jockey.
And thanks, Bingley, for posting something that led to me learning this!