It makes perfect sense that the name Harar comes from the name Erer which is also its river source. Weirdly enough in some sources i see it be called Karanle river.
Is it possible that the name Karanle comes from the Karan basin. Meaning ''With Karan'' ?
This is sketch of upper shebelle made by a Somali Ogaden Sheikh Adamu Bin Mahmuud from Proceedings of the Royal Geographical Society 1884
Along with the erer gate, leadership burials, market place, the oldest mosque and everything you have lined up it points to an eastern foundation towards and connected to Somali inhabited territories.
It's not surprising given the facts that most of the trade, camel caravans carrying goods and urban crafts work was handled by Somalis as we have seen from sources in the 1800s and early 1900s.