Warrants investigation. Crwth has no vowels ( from the Welsh; meaning crowd)...so that's no criterion for dismissing
something as a non-word in English! In fact, Anu did a week of vowelless words once, long before I subscribed. (I know because I thought "crwth" was my best-kept Scrabble secret...but A.W.A.D. already had it documented!)
Gnrr is not in my dictionary, though. But it sounds pretty cool. If it's not a word, it should be!