From an Old French personal name of Germanic (Frankish) origin, derived from wald ‘rule’ + heri, hari ‘army’. This was adopted by the Normans and introduced by them to England, superseding the native Old English form, Wealdhere. It was a very popular name in medieval England, normally pronounced ‘Water’.
English and Scottish: patronymic from the personal name John. As an American family name, Johnson has absorbed patronymics and many other derivatives of this name in continental European languages. (For forms, see Hanks and Hodges 1988.)