Iko Iko (as well as other songs such as Big Chief, Hey Pokey-Way, New Suit, Fire Water) has a very specific meaning. They are all New Orleans Mardi Gras songs about the Black Indians. Black Indians are parade crewes (tribes) that parade through the New Orleans streets on Mardi Gras wearing extravagant ceremonial Indian clothes. They face off when they meet and have battles of clothing, dancing, and singing. The Spy Boy is a ceremonial position (the front runner who scouts out other tribes to do battle with) as is the Flag Boy, Wild Man, and Big Chief. Friends and family who follow are in the "second line" and are therefore second liners. So lines like "My spy boy to your spy boy, I'm gonna set your tail on fire" are ceremonial challenges to the other tribe.
"Joc-a-mo-fee-no-ah-nah-nay, Joc-a-mo-fee-nah-nay" is a ritual chant used by the Mardi Gras Indians which has been around for so long the words are no longer clearly distinguishable, and it has a well understood meaning of its own. Very, very loosely translated it signifies "we mean business" or "don't mess with us". Originally it would have been Cajun (a liberal mix of French and English) and literally translates to "the fool we will not play today".
And stop saying nasty things about my grandma. Both of my grandmothers died within a year of each other. One just after Christmas in '04, and the other just after my wedding in '05. So, for the rest of my life, Christmas and my anniversary will be very painful days for me. Thank you for reminding me of that with your insinuation that my grandma and your grandma were engaged in lewd behavior with each other.