Naniwa is an antiquated name for what is now referred to as the Oosaka region (It was called Naniwa around the 1500s last, if I'm not mistaken).
That being said, In Shinya Shokudo S3E04 (released in 2014), a girl from that area is referred to as "Naniwa musume" by the Shokudou owner, and again as such by some other guys. Why is she referred to as such, instead of using "Oosaka musume"? Is there any particular connotation or something I'm missing about "Naniwa"? Or is it kind of like how, sometimes, people like referring to the Northeast United States as "New England"?