[4] Here Spraclingus is a garbled representation of the byname of Thorgils appearing in later Scandinavian sources,[5] while Ursus is the Latin urso, or bear (Bjørn in Danish, Björn in Swedish).
Saxo further says of 'Thrugillis' that he "lacked not one ounce of his father's valour" (nullo probitatis vestigio a paternae virtutis imitatione defecit).
[10] The chronicle sometimes attributed to the 15th-century John Brompton tells a very similar tale of bear-paternity relating to the birth of Björn Boresune ('bear's son') himself.
[4] In the 18th century, Danish historian Jakob Langebek suggested this bear story was allegorical, and that the brutish 'Wild' Björn, father of Thorgils, was a reference to Jomsviking brigand leader Styrbjörn the Strong (Styrbjörn Starke),[11][12] depicted by sagas as the son of Olaf Björnsson, king of Sweden.
[11][12][13] The sagas relate that Styrbjörn was the first husband of Tyra, the daughter of Harold Bluetooth, king of Denmark and Norway.