(Italian) and (Spanish) form of Theresa. In the English-speaking world the name is often chosen in this spelling by Roman Catholics, with particular reference to the Spanish saint, Teresa of Ávila (Teresa Cepeda de Ahumada, 1515–82).
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.)