Well apparently J Glyn Davies was the writer of the song “Pwy Sy’n Dwad Dros y Bryn”, so it does seem that it was a song about him in that book mentioned above which brought Sion Corn wider fame.
So Sion Corn jseems to join that vast collection of such names and traditions ascribed to the figure brought about and popularised by one persons poem or song.
If you don’t know the song, it is (not surpisingly) a very popular and well-known song about Sion Corn.
Here it is being sung in a traditional manner -
I suppose you want it a little prettier? Oh, go on then!
Oh, all right, here it is again, but this is the last time.
The song which seems to have propelled Sion Corn to fame!
(Not that this invalidates any original connection to corvids, of course!)