While Gorm the Old had disparaging nicknames, his wife Thyra was referred to as a woman of great prudence. Saxo wrote that Thyra was mainly responsible for building the Dannevirke on the southern border, but archeology has proven it much older. Accounts of Thyra's parentage are late, contradictory and chronologically dubious. Saxo holds she was the daughter of Æthelred, King of England (usually identified with Æthelred of Wessex), while Jómsvíkinga saga and Snorri's Heimskringla say her father was a king or jarl of Jutland or Holstein called Harald Klak.