Not any relation to River Bottom and not named after anyone. The dwarven city was named from everyone that arrived here after the great decimation saying "I've reached rock bottom.". This was figuratively and literally. There is a shallow layer of dirt in the area with an extraordinary hard rock below it. The ground was difficult to build on and difficult to remove. Though the dwarves found a way. They somehow understood the rock and could work with it. With almost every other race giving up the dwarves stayed and built their great city. Very little of the rock is ever exported whole. It is only exported in trinkets and tools.