> > Is there any etymological or dialectal explanation for
> > German anthroponyms and toponyms with -TH-, like Orth,
> > Rothenberger, Roth?
Brian is right - or at least has good support.
"Under the influence of Greek and Latin models th and rh became frequent
combinations, especially in the 17th century...." (Priebsch & Collinson,
the German language)