‘White Tusk’
Yskithyrwin
The “chief boar” in Culhwch and Olwen.
As one of his forty tasks, the warrior Culhwch had to obtain one of Ysgithyrwyn’s tusks for Ysbaddaden, the “chief giant”, to use as a razor. Furthermore, the tusk had to be pulled it out while the boar was still alive, and it could only be drawn by Odgar, son of Aedd. It then had to be entrusted to King Caw of Scotland for delivery to Ysbaddaden.
Arthur hunted the boar with his warriors and hounds, and it was Arthur’s dog Cabal and Caw who killed the boar. Caw then brought the tusk to Ysbaddaden and personally shaved the giant with it.
Source
Culhwch and Olwen | Late 11th century