Note 6 — BOOK VI.
Reading edition
—Page 307, stanza c.
Of evil fame was Nannau's antique tree, Yet styled the "hollow oak of demon race."
In the domain of Nannau (which now belongs to the Vaughans) was standing, to within a period comparatively recent, the legendary oak called Derwen Ceubren yr Ellyll—the hollow oak, the haunt of demons.