The Italian surname Forestieri is derived from the word "forestiero," which means "foreigner" or "stranger" in Italian. The name likely originated as a descriptive or occupational surname, referring to someone who was an outsider or a newcomer to a particular place. In Italy, surnames often developed from various sources, including personal characteristics, occupations, or locations. The surname Forestieri suggests that the family may have been perceived as foreigners or newcomers in the area where they resided.