The family name of the author's birth father was Oughtred and he is descended from the Saxons who took the name Uhtred. They had owned Bebbanburg (now Bamburgh Castle in Northumberland) and held it through the Danish invasion and occupation of northern Britain
The relationship between the Danes and the Saxons is thought to also be a link in language. Unlike the need for translators noted in the Vikings series, philologists suggest that the Danes and Saxons could communicate fairly well, much as a Spaniard and Portuguese can in our time with a little effort.
Though used as such by Leofric, the middle English word 'arseling' isn't actually derogatory in nature (or wasn't, back then). It means 'backwards/at the back'. Uhtred usually wears his sword 'arseling' for instance (on his back). This is however most likely where the British word 'arse' comes from.
Ubba in the Last Kingdom is one and the same Ubba who appears in Vikings the son of Ragnar Lothbrok
Shot primarily in Hungary.