The origins of the Gaults in Ireland had centuries ago misted over. Previously of Norfolk – so it was believed within the family, although without much certainty – they had settled first of all in the far western reaches of County Cork. A soldier of fortune had established their modest dynasty, lying low there for reasons that were not known.
Does "misted over" is written figuratively or just mean: covered with mist? it does not seem to me logical because mist covers many cities and then the weather become clear again but the mist does not stay for ever.
And I have never seen "previously" come with "of"! Does it mean: before than Norfolk?
So Dose the whole part mean: even before than Norfolk The origins of the Gaults in Ireland centuries ago was covered with mist?
Source: The Story Of Lucy Gault by William Trevor.