The Barddas of Iolo Morganwg, Vol. I., ed. by J. Williams Ab Ithel, , at sacred-texts.com
367:2 p. 366 This is probably a corrupt reading of "Gwarthefin;" unless we take it as meaning "Gwrthenau," the cognomen of Gwrtheyrn, one of "the three arrant traitors of the Isle of Britain." In that case, the "stratagem" referred to would undoubtedly be the treacherous plot of the long knives on Caer Caradog, of which he was the promoter.
367:3 "Ysgyr," the plural of ysgor, which, according to Llywelyn Sion, is used for a letter, i.e. a notch, or opening, from ys, and gor, an opening, or aperture. There is here clearly a reference to the Coelbren or Peithynen of the Bards, to p. 367 the use of which, under certain national troubles, the people would have to recur, as was the case in the time of Dwain Glyndwr.
367:4 Merddin Emrys was the Bard of Emrys Wledig, or Ambrosius, in the 5th century.