You all seem to say that the Smiths got the name Muirthemne from a place. Perhaps it is the name of a person or thing. Perhaps Muirthemne is:
1)The dwarven name for Wyrd.
2)The Callieach name for Wyrd and the Dwarves based their religion on ancient Calliach texts they found.
3)A Person (Avatar) that taught the Dwarves Magic.
4)An artifact that granted power.
I personally Like the idea that its the name of a God. Perhaps in Dwarven texts Wyrd or the God of Building. The Name taken from the writings of another race like men or Callieach.
-zeph