Originally a variant of Helen, although now no longer associated with that name. Initial H- tended to be added and dropped rather capriciously, leading to many doublets (compare for example Esther and Hester). It is also sometimes used as a short form of Eleanor, to which, however, it is unrelated.
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.)