The Nile river flows south to north originating from lake Victoria. It empties into the Mediterranean sea. The "upper Egypt" simply refers to the highlands( south) as opposed to the delta (flatlands, which are to the north). It originates from their originally being 2 Egyptian kingdoms. Lower egypt(delta, but now northern Egypt on the map) and upper Egypt (the highlands, now part of Southern Egypt on modern maps). The first dynasty and pharaohs United both kingdoms and is thought to be depicted in the https://en.m.wikipedia.org/wiki/Narmer_Palette

They essentially took both kingdoms logo and combined it into one crown you see most pharaohs wearing. https://www.ees.ac.uk/the-royal-crowns-of-egypt