The families with a "Fitz-" prefix go back to some of the supporters and soldiers of William the Conqueror, the first Norman king of England.  William's invasion of 1066 established the unification of England.  The invaders were given land as a prize which was maintained from that period to the present. Beyond that the Fitz prefix is a family name of Normandy, France established by Danish invasions and settlement.  Earliest connections go back to some of the first Danish kings,  Gorm the Old of about 936 was succeeded by his son, Harald Bluetooth. Harald went off each season for raiding and pillaging from Denmark to Normandy.[wikipedia.com]