Please read Alexey Sklyarenko's annotations on Pale Fire, Ada and other Nabokov works here.
Describing the King’s escape from Zembla, Kinbote (in VN’s novel Pale Fire, 1962, Shade’s mad commentator who imagines that he is Charles the Beloved, the last self-exiled king of Zembla) mentions the green, gray, bluish mountains – Falkberg with its hood of snow, Mutraberg with the fan of its avalanche, Paberg (Mt. Peacock), and others: