On February 26, 1996, I received a letter from Professor Oliver Padel of Cambridge. This was in response to a query I had sent him some time earlier in which I proposed that the name Medrawt – born by the personage who died with Arthur at Camlann – may represent the Roman name Moderatus. What Padel had to say on this possibility is important enough for Arthurian studies to be reprinted in full below:
“Not much has been done on the name of Medrawt or Mordred… In an article on various words in Welsh with the root med, Medr-, Ifor Williams suggested that the name might be connected with the Welsh verb medru ‘to be able, to hit’; but he did not develop the idea, only mentioned it in passing.
Middle Welsh Medrawt cannot formally be identical with Old Cornish Modred, Old Breton Modrot (both of which are recorded, indicating an original Old Co.Br. *Modrod), since the Welsh e in the first syllable should not be equivalent to a Co.Br. o there.
What people do not seem to have asked is what this discrepancy means: we can hardly say that Welsh Medrawt is a different name, since it clearly belongs to the same character as Geoffrey’s [Geoffrey of Monmouth] Modredus < Co.Br. Modrod.
Which is ‘right’? I would suggest that the Co.Br. form is the ancient one, and that the Welsh form has been altered, perhaps indeed by association with the verb medru.
That was already my conclusion, but I did not have a derivation for Modrod. However, Modrod would be the exact derivative of Latin Moderatus, as you suggest. Your suggestion is most attractive, and neither I nor (so far as I know) anyone else has previously thought of it.
Like you, I should be relucatant to say that Modrod couldn’t have a Celtic derivation; but it fits so well with Moderatus that I personally don’t feel the need to look further.”
If Medrawt or, rather, Modrod, is Moderatus, this may be significant for a Medraut at Cambloglanna on Hadrian’s Wall, for we know of a Trajanic period prefect named C. Rufius Moderatus, who left inscriptions at Great Chesters on the Wall and Brough-under-Stainmore in Cumbria (CIL iii. 5202, RIB 1737, 166-9, 2411, 147-51). The name of this prefect could have become popular in the region and might even have still been in use among Northern British noble families in the 6th century CE.