Hmmm - let me throw something else in the mix - New Orleans had quite a large Italian immigrant population around the turn of the centruy. In fact, what we now know as the Mafia has it's roots in The Black Hand which is said to have originated there amnongst Italians running the Grocery and food supply trade

Now, I was told as a child, by an aged Italian-American gentlemenwhose family originated in New Orleans that the phrase Giacomo Fi Na Ne was a Black Hand warning about what would happen to you if you squealed about the extortion racket and otherwise strangehold that the Black hand had on the Italian local economy there. He backed this up by telling the mysterious story of the Axe man of New Orleans who chopped up a few local Grocers who didn't pay their protection money. He got the story a little wrong of course, but he said that he heard the phrase uttered both as a brag and as a threat. in other words "Shut up or like Joe - you'll be dead."

I know Giacomo isn't Joe in Itlaian, but my informant always said Giacomo could be translated as Joe and he read it as interchangeable with Joe and John. Guiseppe is Joseph in Italian. Still - it is kinda creepy if you read it as Joe since the name Joseph and St. Josehp's featured heavily in the Axeman Story. Giacomo is often translated these days as Jack but I could see where in the past, it might have been misperceived by non-italians as "joe".

here's a link in case you want to read it.

http://en.wikipedia.org/wiki/Axeman_of_New_Orleans