the earliest recorded use of the patronymic fitzgerald is that of raoul fitz gerald le chambellan, a norman baron, chamberlain of normandy, educator of the young william, future conqueror of england, and father of william de tancarville, earl of tankerville and chief chamberlain of normandy and england after the norman conquest. the eponymous ancestor of the various fitzgerald branches, as well as of the de barry and fitzmaurice families, was gerald fitzwalter of windsor. gerald was a norman adventurer who took part in the 1093 invasion of south wales upon the death in battle of rhys ap tewdwr, last king of south wales. gerald was the youngest son of another norman adventurer, walter fitz otho, william the conqueror's constable for the strategic military fortress of windsor castle, as well as the king's keeper of the forests of berkshire. domesday book records walter fitz otho as tenant-in-chief of lands formerly held by conquered englishmen in berkshire, buckinghamshire, hampshire, and middlesex. walter's positions and most of his lands were inherited by gerald's older brothers, robert, maurice, and william, the oldest, ancestor of the earls of plymouth, while gerald inherited the estate of moulsford, now in oxfordshire, near to wallingford, where his father owned a fortified house adjacent to those of other powerful norman authorities.