Let’s take the Rhine Which goes from Switzerland to Netherlands. When and how did people start agreeing on giving-it the same name ? What about the alps going from southern France to Austria ? When did people agreed that it was the same mountain range ? And obviously what about the Gulf of Mexico ?
There also are multiple rivers with danu root, that also means river: danube, donets, don. People aren’t exceptionally good at naming in general, so “hill” hill and “river” river. 😄
Also town town, mountain mountain, and my favourite, river hill mountain town town.