The name Borknagar is not, contrary to popular belief, an anagram of the word 'ragnarok' with a 'b' added to the front. Rather, as Øystein states, the name was inspired by a fairytale he heard in his childhood about a man who climbed the mountain Loch Nagar; he simply "changed Loch Nagar around a little bit".
Øystein G. Brun says that he doesn't listen to any metal outside Borknagar, but his inspirations come from nature and atmospheric music.