The Brooklyn accent which you do hear in New Orleans talk was explained to me. It had been a question that lingered in my head for a decade after meeting a guy who I thought surely was a New Yorker but to my surprise he told me he was from N.O.
It has to do with the spread of a desease in New Orleans long ago. Perhaps early 1900s...the desease slips my mind but I'm sure a lot of you feepers know what I'm talking about. If not small pox it was something similar. Well, it killed off many people including much of the leadership in the Catholic Church so the Catholic Church imported much of its leadership, including nuns, catholic school teachers...etc. So, the accent caught on.
And that's how the Brooklyn accent came to New Orleans.
Strange, I saw nothing about this in this article.
Yellow fever I believe, in early 1900s.