Thank you, Anneza, for your "harsh words"! I think you are perfectly right. Unfortunately I don't own the book where I found this piece of information and I don't remember its title. But probably the author wouldn't be able to tell where he got the information from. This seems to be a common thing: one author copies information from another without checking it.
This happened in Germany over decades with the name SVENJA. Someone wrote: "female form of SVEN" and dozens of namebooks just copied this, until someone found out that SVENJA was not used as a given name in Scandinavia and that it had nothing to do with SVEN.
So I really appreciate this board because many people with many name books and dictionaries and even more imagination can check out the origins and meanings of names.
On the other hand I have traced bits of information that sounded very unlikely to me - and they turned out to be correct. That's why I put this question on the board.