Runes flash through your head, but they're no longer just pictures. They have meaning, and you understand them. They're commands. Something triggers in your mind, a distant memory unearthed from a past life long since buried. You can see a vast array of runes, far more than Icantha has shown you, and you know their sound and their meaning and how they fit together, the language of Engwith once more at your command.
~ The Watcher re-learns it once more.
Engwithan and Glanfathan are from the same part of the world and are loosely related (as Cornish and Irish are). The ancient Engwythan language (used by the previous residents of Eir Glanfath) is barely understood by even the most well-read scholars. It is based on real world Cornish.