We live in Northeastern US. Many people we know of Italian heritage know about this naming but do not know why. However, some of our Italian friends have never heard of such a thing. We think that this is an Italian-American thing but have never been able to find out why it is done or any background. My husband's name is Vincent but his family always called him "Jim". Same with his father. We have also seen this used by people in advertising / obituaries. They usually say . . . Vincent ("Jim") lastname.