maahey, I couldn't get that glossary to open, but I did find this helpful for brychan:
http://www.genuki.org.uk/big/wal/CMN/Lloyd8.html

edit: fwiw, the Cadfael glossary opens just fine via IE but not with Netscape. from the intersections with the wwftd list and others that are still in common use, I'd say there are few nonce-words or neologisms therein.