The Names of the Isle of Britain
Red Book of Hergest col. 600
1.The first name that this island bore, before it was taken or settled: Myrddin’s Precinct. And after it was taken and settled, the Island of Honey. And after it was conquered by Prydein son of Aedd the Great it was called the Island of Britain.
2. Britain has Three Chief Outpost Islands, and Twenty-seven (others) are subordinate to it. These are the Three Outpost Islands: Anglesey, Man and Lundy. It has Three Chief Estuaries and Seven score subordinate (ones) and Thirty-four Chief Ports, and Thirty-three Chief Cities, and Thirty-four Chief Marvels.
3. The Length of this island, from the promontory of Blathaon to the promontory of Penwith in Cornwall, is nine hundred miles. Its breadth from Crigyll in Anglesey to Sarre is five hundred miles.
4. There should be held therein a Crown and Three Coronets. The Crown should be worn in London, and one of the Coronets at Penrhyn Rhionydd in the north, the second at Aberffraw, and the third in Cornwall.
5. It has Three Archbishoprics: one at St. David’s, the second at Canterbury, and the third at York.
6. Three Realms of Britain: England, Wales, and Scotland.
(in the text: "Teir ynys Prydein: Lloegyr a Chymry a’r Alban")
7. And no one has a right to this island except only the nation of the Cymry, the remnant of the Britons, who came here in former days from Troy.
8. Three Chief Rivers of the Island of Britain; Thames, Severn, and Humber.
9. Three Chief Ports of the Island of Britain: Portskewet in Gwent, the Port of Gwygyr in Anglesey, and the Port of Gwyddno in the north.
This is written just after The Welsh Triads
in the Red Book.
That one of the names of Britain is listed as "clas Myrddin"--Myrddin's Precinct--has lead many scholars to believe that perhaps Myrddin is originally a deity. However, it may also mean "glas myrddin"--the blue-green sea-fort"
The name "Prydein" is actually thought to be cognate with the Gaelic "Cruithan"--the painted ones, i.e., the Picts.
#7 repeats the old tradition that the Welsh are decended of Brutus son of Aneas, making the Britons Trojans. Not particularly likely, however.