This one is a lot older than it sounds. The earliest known version of the tune shows up in an English opera from all the way back in 1706, and it slowly evolved over the next two centuries into a folk song sung on both sides of the Atlantic--with the cow originally saying “boo” instead of “moo”! The farmer wasn't even named MacDonald until a 1925 American recording made the name stick. So the next time you sing “E-I-E-I-O,” you're actually carrying on a tune with more than 300 years of history behind it.