Those nasty rocks to the west of the Shiants, called 'Galtas' or 'Galtachan', might well have an origin in Old Norse. In modern Danish they still have the word 'gavl' (pronounced gowl), meaning gable, or strongest wall, but this is not the relevant word for the Galtas.

Here is the (1959) dictionary translation of the word 'Gal' (pronounced gayl as in Gaelic) followed by the adverb 'Galt'.

It is exactly as Adam has described them in his book!

Also: The suffix, 'As' (pronounced 'ace') is the word for an Old Norse god.
Thor, Odin, you name them; they were all 'aces' (sic).

Therefore, I would expect, (although I am no expert on the subject,) that the name Galtas, roughly translated means mad god and would be pronounced 'Gayltace'