Here is the information we found on the name "Godric of Castlemont."
Godric is definitely a period name. The "Oxford Dictionary of English Christian Names" says:
[Godric] was very common in England before the Norman Conquest. The Normans used it as a nickname for an Englishman, and called Henry I and his queen Godric and Godiva, in allusion to her English blood and his supposedly English sympathies."
It goes on to say that Godric died out in the course of the 13th and 14th centuries.
"Castlemont" is a typical Norman place-name. "Castle" and "mont" were introduced into the English language by the Normans along with many other words of French origin. "Castlemont" would be a very plausible English place-name, but only after the Norman Conquest of 1066. In most written English records after this time, "de" was used instead of "of," although some examples of "of" have been found.
So the name "Godric de Castlemont" or "Godric of Castlemont" is a plausible English name for the period from roughly 1100-1350. For a persona from the 9th century, it would be better to look for an Old English by-name.
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If you would like assistance finding a by-name, or with anything else, we would be happy to assist you.
Academy of S. Gabriel