A hypothesis for the name 'Boneless' for Ivar is that it was was actually 'the hated', which in Latin is called Exosus. A medieval scribe with a basic knowledge of Latin could easily have interpreted it as ex (without) os (bone), thus "the Boneless". It is generally regarded, though, that Ivar was physically disabled. Also 'boneless' could simply refer to him being impotent, and not otherwise disabled.