 Use of the prefix "Don" as a style for certain persons of distinction spread to the Kingdom of Naples and Sicily during the Spanish domination of southern Italy in the 16th century.Officially, it was the style to address a noble (as distinct from a reigning) prince ("principe") or duke ("duca"), and their children and agnatic descendants.Any Italian monarch (as in Spain) might informally be addressed or referred to with this prefix, for example King Carlos III of Spain was widely known in his Neapolitan realm as "Don Carlo".