Mogthrasir

Greetings all,

Delurking again for my bi-annual question:

Could anyone help with an etymology and meaning behind the Norse name
Mogthrasir?
The name is documented in the Vafthrudnismal 49.
It is often explained as meaning "striving for sons" but I question
this.

Mog is defined in the Rigsthula as meaning "kinsman".
Thrasir is defined by Rudolf Simek as meaning "the furious one"
or "the threatening one".

So I question does Mogthrasir mean "striving for sons" or "furious
at/threatening the sons", or something else entirely?
When examining the Vafthrudnismal, the name seems to be used to
describe the father of the Norns, thus is there any meaning or
etymology which might be more apt?

As always, any help would be greatly appreciated!!

Regards,
Aydan