Yes its that god araxes probably started the trend. Im not sure if its a sythian god or the god of a people conquered by sythians. His daugther always seemed to me like she was not indoeuropean.

Basicaly true nomads dod not appear in the steppe until horses were big enough to ride about 1000bc. Before these while there were people living in the steppe they were not true nomads, had small scake societies, and were only living in certain parts that permited either limited agriculture or hunter gathering. I still dont kbow why since they still used oxen to carry teir wagons. It maigth have something to do with the productive contextof hearding and cattle raiding.

Its very likely these people were some sort of old iranian. Sythians or a really similar variety. Its also likley the tradition of taking regnal names based on large bodies of water and many other stepe mythological and political traditions started here.

So while later nomads were of diferent ethnic and linguistc makeup they still borrowed the technologichal kit and some of their cosmology from the previous group of nomads. To the point that many of their ethnogenesis myths are really similar. So they are all share the same cultural ancestor who is named after a river.

That being said i have seen some soviet era genealogies were they indeed claim all these people share a common ancestor. But that is dubious. I meant it an a softer cultural tradition sence rather than direct genetic decent.