A Viking Jarl's wife would be referred to as a "Frilla." She would be addressed as "Frilla" or "Frilla [Jarl's name]." Her title would be “Frue” and she would be addressed as “Fru”, as in e.g. “Fru Inger til Østråt” (Lady Inger of Ostrat ), which is still what we use in Norwegian, Swedish and Danish.