> Probably also from similar names in a family. But we should not
> forget that no Germanic etymological study existed. We see that, for
> example, both Ari Thorgilsson and Snorri Sturluson give wrong
> etymologies in the only steads that I know of, one each

Here's one from Eyrbyggja saga:

"Hrólfur var höfðingi mikill og hinn mesti rausnarmaður. Hann varðveitti
þar í eyjunni Þórshof og var mikill vinur Þórs og af því var hann Þórólfur
kallaður."

Kveðja,
Haukur