What is "e-i-e-i-"

"E-I-E-I-(Annoyed Grunt)" is the fifth episode of the eleventh season of the American animated sitcom The Simpsons. It originally aired on the Fox network in the United States on November 7, 1999. In the episode, inspired by a Zorro movie, Homer begins slapping people with a glove and challenging them to duels. However, when a real Southern gentleman accepts Homer's request for a duel, the Simpsons run off to the old farm Homer lived in with his parents and breed a dangerously addictive but successful tobacco/tomato hybrid called "tomacco". Just when they are about to gain a hundred and fifty million dollars from the hybrid, dangerously addicted animals ruin their plan.