Here we go, (note this is from memory, I don't have the book with me.)
The song was sung in the south after the Civil War. It was sung on some southern stage, perhaps New Orleans, or South Carolina. It was somewhat like a minstrel song/performance.
The crowd begged that it be sung over and over again. On either the opening night or sometime subsequent, the singer came to the verse:

"But when so near we saw them wink
We thought it time to pop them
And it would have done you good I think
To see Kentucky pop them!"

And, when he sang this verse, he moved his arms in front of his torso and pretended that he had a rifle in his hands and was firing it.
During one of his performances, when he got to this verse, someone from the audience threw a (sharp) utensil at his head; the singer was quite frightened because it came so close to his head, that he stopped the performance and bowed and left the stage. Later on, an older man met him to apologize to him; the older man explained that he was one of the soldiers under Jackson during that fight in New Orleans and he was so excited when the singer came to that verse "To see Kentucky pop them" that the older man threw his hands out in a burst of enthusiasm and accidentally let go of the metal utensil he was holding in his hand."

(Sorry it took so long to relate this, I don't have an Internet at home and have to go to the public libraries....)

SOURCE: A TREASURY OF MISSISSIPPI VALLEY FOLKLORE, B.A. BOTKIN