I can give you a quote from Mac Lysaght's The Surnames of IRELAND,"A number of Hiberno-Norman names begin with FITZ(French 'fils')Fitzgerald is the best known of these: it is called MAC GEARAILT in Irish.The almost equally well known Fitzpatrick ,however is not of Norman origin but is the Gaelic MAC GIOLLA PHADRAIG normanized." There appears to be no rule that fits all,but in most names that I have seen FITZ denotes Norman origin. Take care, Joe Coastal CarolinaUSA PoppaJoe@webv.net