1911 Encyclopædia Britannica/Gellert
GELLERT, or Killhart, in Welsh traditional history, the dog of Llewellyn, prince of Wales. The dog, a greyhound, was left to guard the cradle in which the infant heir slept. A wolf enters, and is about to attack the child, when Gellert flies at him. In the struggle the cradle is upset and the infant falls underneath. Gellert kills the wolf, but when Prince Llewellyn arrives and sees the empty cradle and blood all around, he does not for the moment notice the wolf, but thinks Gellert has killed the baby. He at once stabs him, but almost instantly finds his son safe under the cradle and realizes the dog’s bravery. Gellert is supposed to have been buried near the village of Beddgelert (“grave of Gellert”), Snowdon, where his tomb is still pointed out to visitors. The date of the incident is traditionally given as 1205. The incident has given rise to a Welsh proverb, “I repent as much as the man who slew his greyhound.” The whole story is, however, only the Welsh version of a tale long before current in Europe, which is traced to the Indian Panchatantra and perhaps as far back as 200 B.C.
See W. A. Clouston, Popular Tales and Fictions (1887); D. E. Jenkins, Beddgelert, its Facts, Fairies and Folklore (Portmadoc, 1899).