I lived in New Orleans for some years, and second-lined with plenty of Injun tribes. I'd listened to the Wild Tchoupitoulas records and sung along with the Grateful Dead for years before I headed to the City that Care Forgot. The main influence on what things "mean" in New Orleans is that it's not limited by the purely rational - it's poetry. Poetry is the most meaning in the least language. New Orleanians today are largely illiterate (truly: close to 50% cannot read nor write), and have usually been even less limited by literal definitions throughout three centuries and more.

So many of the meanings in this thread are at least relevant, even some that are contradictory when confined within a 21st Century American public education. Especially the ones consistent with African and Italian roots: the recordings from Cosimo Matassa's 1940s and 1950s studios where Black culture was first recorded (and where I lived generations later) are more fingerprints from the scene. Of course everyone knows New Orleans is mixed up French, but it was Spanish for 34 years after and before the French ran it. Flirty double entendres, cunning secret codes, inside jokes especially about outsiders, conflations, resonances, repetition for its own sake, transcendent symbols: this is Nawlins.

Among the second-liners - whether paraders, musicians, feathered Injuns, stumblebums or E. all of the above - "Jacomo fi na nay" was taken to mean "out of the way, fool": the operative meaning when a parade comes up the street you're standing in. But indeed its more literal meaning is in the song Brother John. "If you don't like what the Big Chief say / You just Jacomo fi na nay" = "You're just dead, fool". Same difference, as we Yankees say before they tame us in school.

Mardi Gras parades were fun, central cultural drumbeats of one of the most mixed cultures in the world. They were also battlefields, with tribes shooting and cutting each other while fired up on song, liquor, vendettas and voodoo (and everything else within reach in that global port). "Out of the way fool" is just a modulation of "you're dead fool" when the tribe comes through. "Ah nah nay" probably is connected to "andante": "get to steppin'", again in a fuzzy association defined by the urgency of the street more than by a dictionary.

Now, who knows what "handa wanda" means?