Moreover, the question of Germanic Tribes and their relationship to place names is entirely chicken/egg. Traditional German historiography, most notably the works of Ranke?, tend to argue a thing's inherent "Germanness" on the grounds that clearly work in a 19th century nationalist context, but hardly work for today's historians. To argue that the people living in Silesia when it was taken by the Slavs (AFTER it had been overrun by Vikings and others) were the same ethnic group as those living in Silesia in 1945 is insupportable.
Silesia was in earlier centuries overrun by Slavs and again in 1945. The Communists ousted most of the Silesians. Some Silesians managed to stay in their homeland, while it was taken over by Poland.
The Polish name today for Silesia is Slask?.
60 years later some book writers are finally heard at amazon.com on this Silent Ethnic Cleansing