Please read Alexey Sklyarenko's annotations on Pale Fire, Ada and other Nabokov works here.
Describing his wife, Queen Disa (Duchess of Payn, of Great Payn and Mone), 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) quotes a Zemblan saying belwif ivurkumpf wid spew ebanumf ("A beautiful woman should be like a compass rose of ivory with four parts of ebony”):