Oh that refers to Salt Pork, a method and final product of preserving pork before refrigeration was widely available. It was INCREDIBLY salty and likely needed to be soaked for hours before preparation to begin with to reduce its salt content, if anything. This slow cooking method would allow even more of the salt to be exuded from the meat and season the rest of the ingredients. I'm assuming this all gets stirred together at the end of the recipe into a bean stew much like Brazilian Feijoada.