Yes, Wend, Wende and Wendt, all German surnames with this meaning. However, I don't think the term Wend covers a tribe as such. It seems to have been a dismissive term for speakers of a language other than one's own, a bit like the Greek word Barbarian, all those people who can't talk properly and just go "ba-ba". It seems that the word ethnic term Finn is the same word, while the Finns have a related word to identify the Russians. Whatever the linguistic origins the term came to be considered offensive in modern Germany, and that other word, Sorb, is now the label of choice.