Liddington Castle (Badbury)
Breguoin is, certainly, for the Brewyn of the Urien poems, i.e. the Bremenium Roman fort. All my attempts to make something else of it have failed. As Dr. Simon Rodway of the University of Wales succinctly states,
"It's from Bremenium. The <gu> stands quite regularly for /w/, and the oi for the diphthong /ui/ < /e:/, a spelling which is found elsewhere in Old Welsh. All this is explained quite clearly by Kenneth Jackson. There is nothing controversial about this derivation."
Brean in Somerset appears to have preserved the Breon spelling. Early forms for Brean are Brien, Breen, Broen, Bren, Breon. And Brean Down boasts a promontory fort, as well as other ancient structures, including a Romano-British temple ( http://www.pastscape.org.uk/hob.aspx?hob_id=1065575&sort=4&search=all&criteria=brean%20down&rational=q&recordsperpage=10, http://pastscape.org.uk/hob.aspx?hob_id=191302&sort=2&type=HILLFORT&typeselect=c&rational=a&class1=None&period=None&county=100248&district=None&parish=None&place=&recordsperpage=10&source=text&rtype=&rnumber=).
Unfortunately, the glossator is plainly wrong. Breguoin does not stand for Bregion.
I think there is a rather simple solution to this problem. Only several miles north of Bath is the Bury Camp or Bury Wood Camp, a major hillfort:
This hillfort is between the By Brook and its two tributaries the Doncombe Brook and the Lid Brook. It is also very near the Roman road known as the Fosse Way. Now, as it happens, Lid is from OE hlyde, 'loud', and as Ekwall and others have made clear, the meaning was something like "the roaring brook". Bremenium has the British root *brem- (cf. Welsh bref), and as found in Bremenium was named for a stream near the Roman fort that has the exact same meaning, i.e. it was "the roaring stream." There is an Afon Brefi and a Roman fort Bremia in the Cardiganshire of Ceredig son of Cunedda.
I would make a case, then, for Breguoin (Brewyn, Bremenium) being a Welsh rendering of the Lid Brook name, and as a hill-name is would stand Bury Wood Camp to the north of the Lid Brook.
A NOTE ON LIDDINGTON CASTLE/BADBURY
Readers of my book THE ARTHUR OF HISTORY and of previous blog entries posted here will be familiar with my comprehensive discussion of the place-name Badon as it relates to OE bathum, 'baths', and to baddan(-byrig). In brief, there is not a single Celtic linguist who will allow Badon to have come from Baddan-. All insist the form comes quite regularly from bathum.
Recently, I made an attempt to derive OE Baddan- (from a supposed personal name Badda, although other ideas have been proposed) from an original Brythonic source. This effort also failed. To summarize why Badda/Baddan- can't come from the British, here is what Professor Richard Coates sent me:
British */t/ > Britt. */d/ would show up as OE /d/, not as a geminate (double).
British */tt/ > Britt. */θ/ would show up as OE */θ/, written with thorn, but never <dd>.
British */d/ > Britt. */ð/ would show up as OE /d/ or /ð/, depending on the period, for which the spelling <dd> is most unlikely.
British */dd/ seems to have yielded simple Britt. */d/ (Jackson LHEB 428, on credu), and would show up as OE /d/, not as a geminate (double).
So I conclude that Badda cannot be of Celtic origin, particularly because Late British did not have geminate /dd/."
However, I should point out what would otherwise appear to be an odd coincidence. The Liddington name, as applied to the Badbury/Baddanbyrig hill-fort near Swindon, also means "loud or roaring stream." This would, then, match the meaning of Breguoin just as a fort on the Lid Brook might have done. In the past I have pointed out that the Barbury or "Bear's Fort" near Liddington/Badbury could be an early English reference to Arthur, as his name was connected by the Welsh with their word arth, 'bear.' Furthermore, Wanborough near Liddington was in the Romano-British period called Durocornovium. This place-name contains the same word we find in the tribal name Cornovii and in Cernyw, the Welsh name for Cornwall. Welsh legend consistently associated Arthur with Cornwall.
It seems inconceivable that Gildas's spelling for Badon - and every subsequent spelling - is incorrect. Yet it is tempting to see in Agned (Agued), Breguoin and Badon a typical Celtic triad of names all designating the same very important hillfort. But if this is so, someone much sharper than I am will have to be able to philologically and phonologically demonstrate to the satisfaction of the linguists how Badon could stand for Baddan-.