Saxi was originally a byname derived from Old Norse noun sax ‘short, one-edged sword’, but possibly in some instances derived from an ethnonym from the name of the Saxons.

An original East Scandinavian name, it is fairly common in Sweden and very common in Denmark. The name is rare in Iceland, although it is borne by one individual in the settlement period (c. 870-930). Although common in Eastern Norway, there is only a single instance of the byname Sax is recorded in West Scandinavia in the tenth century. Saxi is found in several place-names in Normandy.

It is well-attested in Lincolnshire and Yorkshire although some forms may represent the Continental Germanic male personal name Saxo. Occasionally it is difficult to determine whether the first element in place-names such as Saxby All Saints, Lincolnshire and Saxby, Leicestershire is Saxi or the Scandinavian genitive plural form of an ethnonym: Old English S(e)axe, Old Norse Saxar ‘Saxons’.