Feminine derivative of Gerald, invented in the 16th century by the English poet the Earl of Surrey, in a poem praising Lady Fitzgerald. It remained very little used until the 18th century, when it suddenly increased in popularity.
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.)