Math fab Mathonwy

In Welsh mythology, Math fab Mathonwy, also called Math ap Mathonwy (Math, son of Mathonwy) was a king of Gwynedd who needed to rest his feet in the lap of a virgin unless he was at war, or he would die. The story of Math is the fourth book of The Four Branches of the Mabinogi.

The Mabinogi of Math

Math is tricked by his nephews

Math's nephew Gilfaethwy had become obsessed with Goewin, Math's footholder. The magician Gwydion (Gilfaethwy's brother), devised a plan to make Goewin available. Gwydion told his uncle about an animal that was new to Wales, called pigs, and how he could get them from their owner, Pryderi of Dyfed. He took a band of men, including his brother, to Ceredigion, where they disguised themselves as bards to gain audience with King Pryderi.

Gwydion was a skilled cyfarwydd (storyteller) and regaled the court with his tales. Having charmed the king, he offered to trade the pigs for some horses and dogs, which he had conjured through magic. Pryderi agreed to the trade and Gwydion and his men took the pigs back home to Gwynedd, but his trickery was revealed and Pryderi waged war against Gwynedd. While Math went to battle, Gilfaethwy raped Goewin.