"Iko Iko" (The Dixie Cups)

No one seems to know for sure what "Iko Iko" is about.  Anyone from New Orleans I've ever asked has had his/her own unique take on it.  Some will say it's a taunt from one parade krewe to another at Mardi Gras: "Hey, you!  Kiss my ass."  Others will say the phrase is actually jock-a-mo, which means "it's very good" in the extinct Mobilian dialect, which Native Americans and early French colonials along the Gulf Coast used as a trade language.  Then again, you get other interpretations, like my former co-worker's: "It doesn't mean anything; it's just something you holler to get some beads."
Whatever "Iko Iko" means, The Dixie Cups (a 60s girl group out of New Orleans, originally consisting of sisters Barbara Ann and Rosa Lee Hawkins and their cousin Joan Marie Johnson) cut a pretty definitive version of the song in 1965 with Jerry Leiber and Mike Stoller.
The group was in the studio with Leiber and Stoller, working on several tunes after the success of their most famous single, "Chapel of Love."  They'd done a few takes and everyone was taking a short break when the ladies started joking around, banging on ashtrays and an empty Coke bottle with drumsticks, while singing the Mardi Gras song their grandma had taught them.  Luckily, the tapes were still running and captured the whole performance.
Leiber and Stoller liked the impromptu song so much that they overdubbed upright bass and released it as a single: "Iko Iko."
A couple of years later, they got sued by James "Sugar Boy" Crawford, whose 1954 song "Jock-A-Mo" clearly was the basis of "Iko Iko."  (For all the ladies knew, it was just a traditional New Orleans song or something their grandma had made up.)
Crawford's own take on the phrase was that it was something Mardi Gras Indians (inner city Carnival krewes with a long, fascinating history) would chant when settling scores with rivals, as he conveyed to Offbeat magazine in 2009:

"It came from two Indian chants that I put music to.  'Iko Iko' was like a victory chant that the Indians would shout. 'Jock-A-Mo' was a chant that was called when the Indians went into battle.  I just put them together and made a song out of them."