Posted on 11th November 2016 by melyn Gwethheans is the Cornish word for deterioration Yes, deterioration in Cornish is gwethheans Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related Post navigationPrevious post: Dismygriv is the Cornish word for estimateNext post: Gwyns is the Cornish word for winch