Before the unified Egypt there was a couple of places like Cheni, Nubut and Néjen and it is likely that Cheni's people gained the control of territory and from that moment on they occupied the area of Egypt. Also, according to "Faraones" by History Channel it is believed that Narmer is the first pharaoh. Even if Narmer came from Cheni, the idea of the pharaoh also came from there or is it product of several cultures?
Pharaoh is the Term people use to refer to the leader or king of Egypt. Pharoah is not that different from a king. The term Phaora is just pure language and not a "New Invention".