A medieval scribe with only a basic knowledge of Latin could easily have interpreted it as ex (without) os (bone), thus "the Boneless",[5] although it is hard to align this theory with the direct translation of his name given in Norse sources.
[6] He is often considered identical to Ímar, the founder of the Uí Ímair dynasty, which at various times, from the mid-ninth to the tenth century, ruled Northumbria from the city of York, and dominated the Irish Sea region as the Kingdom of Dublin.
In the original 11th-century manuscript, the subject of the entry was simply called righ Lochlann ("the king of Lochlainn"), which more than likely referred to Ímar, whose death is not otherwise noted in the Fragmentary Annals.
The cause of death—a sudden and horrible disease—is not mentioned in any other source, but it raises the possibility that the true origin of Ivar's Old Norse nickname lay in the crippling effects of an unidentified disease that struck him down at the end of his life.
In 1686, a farm labourer named Thomas Walker discovered a Scandinavian burial mound at Repton in Derbyshire, close to a battle site where the Great Heathen Army overthrew the Mercian king Burgred.