Another interesting passage from Bartlett’s endlessly interesting The Making of Europe:
In the early Middle Ages most regions of Europe had highly localized repertoires of names. It is easy, given a few personal names, to tell which region or ethnic group is being talked about. Among aristocratic Germans it is even possible to make a good guess at the family, so distinct and particular are the naming patterns. Those who moved permanently from one linguistic or cultural world to another would feel the pressure to adopt a new name, as a tactic designed to avoid outlandishness. On his arrival in Normandy in 1085, for example, the child oblate Orderic was renamed: ‘the name of Vitalis was given me in place of my English name, which sounded harsh to the Normans’. When noble ladies married into foreign royal families who spoke a different language, it was not uncommon for them to adopt a new name. The Bohemian princesses Swatawa and Markéta became, respectively, the German countess Liutgard and Dagmar, queen of Denmark. Henry I of England’s wife was ‘Matilda, who had previously been called Edith’. The tight bonding of name and ethnic or local group explains the pressure for such diplomatic renaming.
The same intense regionalism is true of saints. Their cults usually had one or two main centres, where the chief relics were situated, surrounded by a limited zone of relative cultic density where one might expect to encounter churches devoted to the saint, perhaps subsidiary relics and men named after the saint, a zone which shaded off into the zones of other adjoining local saints. If we find a town whose churches are dedicated to Saints Chad, Mary and Alcmund, we know we are in the English Midlands (the example is Shrewsbury). This regional concentration is characteristic even of the more successful cults. For example, though there were over 700 churches dedicated to St Remi, 80 per cent of them were located within 200 miles of his chief centre at Rheims. The historian Charles Higounet mapped the places named after the saints of Merovingian Aquitaine and found that they stopped abruptly at the Loire, the Rhône and the Gironde.
In the eleventh and twelfth centuries this highly compartmentalized world began to change. A circulation of names and saints through the system began. Sometimes this occurred as a result of conquest. England provides a neat example of such a change. In 1066 the country was conquered by an army of French-speakers from northern France. Within a few years that army had transformed itself into a landed aristocracy — a French-speaking aristocracy ruling an English-speaking peasantry. Not only did the two groups speak different languages, they bore different names. Although Norman and Anglo-Saxon nomenclatures were both, in origin, Germanic, the two countries had developed quite different repertories of names. English Ethelreds, Alfreds and Edwards faced Norman Williams, Henrys and Roberts. In the eleventh century the distinction is fairly watertight: a name is a virtually certain indicator of ethnic origin. In the twelfth century this situation changed. Names are, of course, among the most malleable elements of linguistic culture, offering, as they do, the repeated chance of choice; and soon, it seems, the English population of England chose to adopt the names of their conquerors. The kinds of pressure at work are shown by the story of one young boy, born in the area of Whitby around 1110, whose parents initially christened him Tostig but, ‘when his youthful companions mocked the name’, changed it to the respectably Norman William. This process began among the higher clergy and townsmen. […]
Our picture must, however, be complicated by one more factor. […] Simultaneously changes were taking place in the very pattern of naming and worship of the saints throughout Latin Christendom. Everywhere the universal saints and the dominical cult were increasing in importance. The apostolic saints, especially Peter and John, the Mother of God, and God himself, as Trinity, Holy Saviour or Corpus Christi, were eclipsing the local shrines and cults of earlier medieval Europe. In the twelfth century, for example, the churches of Wales adopted universal saints, like Mary and Peter, as additional patrons, to reinforce their obscure local saints. […] And, following in the wake of their rise to prominence, European naming patterns began to homogenize as parents, kin and priests began to choose names for children from these universal saints. The highly localized name repertoires of the early Middle Ages were replaced by a more standard pattern in which the universal saints were increasingly common.
One wishes the medieval English hadn’t been quite so fond of the name Matilda; Henry I’s mother, wife, and daughter were all named Matilda, as was his nephew Stephen’s wife and one of his son Henry’s daughters. Between the Williams and Henrys and the Matildas and Eleanors, it all becomes very confusing.