They took it from the Kievan Rus, yes, but it's more Ukraine than Russia
There was no Russia, no Ukraine, just Rus. Equally belonging to Ukraine, Belarus and Russia.
When did Poland reach the Elbe? I think they had helter-skelter control of west Pomerania at one point, and that's it.
What I m saying is that this part of Lithuania-Ukraine-Belarus was Polish for a long time and it was considered like naturally Polish land, so it should use Polish names
We are going to use Lithuanian names for Lithuanian kingdom and Polish names for Polish kingdoms, don't worry.
Also, Germany controlled Slask, Pomerelia for a very long time. Should they consider it German?