The conventional thing in the past has been to identify the origin of the name Beaumont (applying to people from the Cotentin) with Beaumont-Hague, west of Cherbourg.
But I had noticed that many of the early Beaumont references (twelfth and early thirteenth centuries) were to a group of places east of Cherbourg, including Neville-sur-mer, Fermanville, and Cosqueville. I then spotted that there is a place called Beaumont in or near that group of places, where there is a substantial perhaps seventeenth century house called the Manoir de Beaumont.
From Beaumont-Hague to le Manoir de Beaumont is about forty kilometres whereas the other places associated with these Beaumonts are all within five or six kilometres of one another.
It did not seem to make entire sense to associate the east side people with Beaumont-Hague, but I now need to reconsider that.
The main reason for this is that I realised I had references which look entirely sound, to the effect that a certain Juhel de Bellomonte was patron of the church of Bello Monte (certainly here meaning Beaumont-Hague) in the mid-thirteenth century (this being from the Livre Noir, or Black Book, of the Diocese of Coutances).
Also from the Black Book Juhel de Bellomonte was patron of the church of Cosqueville, whilst a Guillaume (William) de Bellomonte was patron of the church of Fermanville.
This makes Juhel - surely there cannot have been two of that name at the same time - to be a proprietor both west and east of Cherbourg. That removes the reason for thinking the origin must be east side, and leaves me thinking it could be either.
There may well be other Beaumont references (various first names) that can be confirmed as west side and I believe there are further references to the name Juhel (and certainly other names) that can be confirmed as east side.
It is said in several books etc that during the fourteenth century both Beaumont-Hague and the places east of Cherbourg were in the hands of people called d'Argouges, one of whom had married an heiress called Thomasse de Beaumont, in 1332.
Deciphering the genealogy may well be impossible, but suggestions might be along the lines that there were related families - cousins using the surname Beaumont - based both west and east of Cherbourg, and that by one or more inheritances it all came in the end to Thomasse and her husband.
Moreover I think that this family (in the wider sense) was divided by the separation of Normandy from England in 1204, and that there was at least one branch of it in England, as I have hinted before.
EMB 9-10 October 2023
Notes:
A parish by parish summary from the Livre Noir is printed in the Recueil des Historiens de la France vol. 23 (Paris, 1894) from page 493, with Beaumont-Hague at p.528 (Juhel), and Fermanville (Willelmus, Guillaume), and Cosqueville (Juhel) at p.531.
There is an incorrect statement that Guillaume de Beaumont was patron of both Cosqueville and Fermanville in Louis Drouet's book Recherches Historiques sur les Vingt Communes du Canton de Saint-Pierre-Eglise, at p.253 repeated at p.278, citing the Livre Noir. That book is not concerned with west side places, though in passing, it does mention Beaumont-Hague as one of the places the family had lands (pages 280 and 409).
An article in Memoires de la Societe Nationale Academique de Cherbourg, 1871 (Pouilles Inedits de la Hague et de Carentan, collected & translated by M. de Pontaumont) contains the same information from the Livre Noir about Beaumont-Hague, and adds that the Livre Blanc (White Book) of c.1340 shows that the church was then held by the heirs of Juhel. That article is not concerned with Cosqueville etc.
An example which I came across just after writing the above, which seems to both reinforce the early association with Beaumont-Hague, and to suggest that a member of the family had opted to go to the English side, is a charter of king Philip Augustus dated 1207 in which he granted all of the land of Richard de Bello monte in Hague (Haiga) to a new holder (Cartulaire Normand no. 161).
