The latest article by Edmond Valin examines the FBI’s fairly abrupt adoption of the term “La Cosa Nostra” in the early 1960s to refer to traditional Sicilian-Italian organized crime. Valin digs through FBI records to turn up the earliest sources of the term and considers the reasons it may have been preferred by federal authorities over the traditional term, “Mafia.”
http://mafiahistory.us/rattrap/mafialacosanostra.html