Usual English form of Dorothea. The name was not used in the Middle Ages, but was taken up in the 15th century and became common thereafter. It was borne by the American film star Dorothy Lamour (1914–1996, born Dorothy Kaumeyer).
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.)