One piece of info that might provide some insight: There are actually three interconnected lakes, with Pontchartrain in the middle - Lake Maurepas to the west, Lake Pontchartrain, and Lake Borgne, which is actually open to the Gulf of Mexico.

Madisonville, formerly known as Cokie ("coquille", or seashell) and located just off the north shore of Lake Pontchartrain on the banks of the Tchefuncte River, is historically a Creole (in the mixed-race sense) town. I like to imagine that our anonymous Irishman fetched up there and met his Creole girl.

I like the Tanyas' version too. That gal sings like she might even be from south Louisiana...