Norman Surname Protocol

To appreciate this early Norman surname protocol the primogeniture must be understood. It is the foundation of most locative names in Britain. 

During the lifetime of the father it was very uncommon for any family member to also use that same surname. The chief paternal domain name could not be used except where, unusually, it was used in both Normandy and England, but even on this rare occasion it was customary to append a I, II or III to the son's surname in England to differentiate from the parent in Normandy. 

On the father's death the eldest son would inherit all, including the right to the surname both in England and Normandy or Brittany. The younger sons usually adopted the locative surnames of their own new domain, such as Mallbank above, even though he is described as the Baron of Nantwich, hence the backtrack relationship, between father and younger sons became tenuous, and difficult to link. 

On the eldest son's death, the rights went to his sons, unless childless, in which case it went to the next youngest son of the father, and he changed his surname from the locative name which he had used for part of his life. Nor were locative surnames taken lightly. These would be as important, legally, as the knight's seal, and became his domain name. They were charter proof of entitlement to his holding, his new domain. 

Most younger sons would never get to use the family surname. Fitz names, prefixing the font name, were believed to be a sign of bastardy, or, in those days known as 'natural' sons. However, a more plausible explanation, might be that of a younger son who did not hold a domain, and could not use his father's surname until after the father's death. Hence, Fitz became a temporary surname, which sometimes held in its own right.