Contrary to popular belief, this is not a Grateful Dead tune!
Many iconic rock and roll bands like the Dead and the Allman Brothers were largely formed by their experiences playing in New Orleans. The Beatles too received a massive does of New Orleans sensibility via the records of Fats Domino. ("Ain't That a Shame" was the first tune John Lennon learned to play.)
"Iko, Iko" is an old street tune. The coded language goes back to before the days of Jelly Roll Morton and comes from the "Mardi Gras Indian" tradition which probably goes all the way back to Congo Square and is the longest continually performed black music in America.
Dr. John, jazzman turned pop funkster, tones it down so students can watch and get some clue as to the complexities of everyday New Orleans keyboard polyrhythm.
Never did a city produce so much music and was so underrated,.