Ivar the Boneless
Ivar the Boneless (Old Norse: Ívarr hinn Beinlausi; Old English: Hyngwar) was a Viking leader and a commander who invaded what is now England. According to the Tale of Ragnar Lodbrok, he was the son of Ragnar Lodbrok and Aslaug. His brothers included Björn Ironside, Halfdan Ragnarsson, Hvitserk, Sigurd Snake-in-the-Eye and Ubba.
The origin of the nickname is not certain. The sagas describe him as lacking bones. A genetic condition, osteogenesis imperfecta, is known to cause the body to appear to have "an imperfect bone formation", because the body and limbs can bend off beyond the usual joints limitations, and produce other ill effects and degrading functions. It was known by the Ancient Greeks and Romans. It could also be that he had what we now call Ehlers Danlos, which causes recurrent joint dislocations and joint hypermobility, and is a genetic collagen deficiency. They reported that it was common in the British Isles, but little was understood until the early 1900s. According to the Tale of Ragnar Lodbrok, Ivar's bonelessness was the result of a curse. His mother Aslaug was Ragnar's third wife, She was a völva. She said that she and her husband must wait three nights before consummating their marriage after his return following a long separation (while he was in England raiding). However, Ragnar was overcome with lust after such a long separation and did not heed her words. As a result, Ivar was born with weak bones.
Another theory is that he was actually known as "the Hated", which in Latin would be Exosus. A medieval scribe with a basic knowledge of Latin could easily have interpreted it as ex (without) os (bones), thus "the Boneless", although it is hard to align this theory with the direct translation of his name given in Norse sources.
While the sagas describe Ivar's physical disability, they also emphasise his wisdom, cunning, and mastery of strategy and tactics in battle.
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.