What is "caffo"

Caffo was a sixth-century Christian in Anglesey, north Wales, who is venerated as a saint and martyr. The son of a king from northern Britain who took shelter in Anglesey, Caffo was a companion of St Cybi, and is mentioned as carrying a red-hot coal in his clothes to Cybi without his clothes getting burnt. After leaving Cybi, Caffo was killed by shepherds in the south of Anglesey, possibly acting in retaliation for insults Caffo's brother had paid to the local ruler. The area where he died has a village, Llangaffo, named after him, as well as the parish church of St Caffo, Llangaffo.