This is a simple vegetarian dish. According to the Accademia Italiana della Cucina, it's "typical of Caserta", a humdrum little town northeast of Naples with an immense and fabulous palace and gardens. I don't know why this simple dish has such specific roots, but there you have it. It's delicious in any event.
We visited Caserta in 2015 to see the royal palace of the Bourbon kings, and I recommend it!