The Celts and Their Pigs:
Pigs were a very important part of the Celtic economy and society in Western Europe. Pigs were associated with the Otherworld, the feasts of the dead, and as symbols of abundance. Swineherds or pig keepers were thought to be magicians. In Irish folklore, swineherds could cross from the Otherworld to this world and return again. The Lord of the Otherworld was normally portrayed with a pig over his shoulder. The Celtic goddess of crops and abundance, Caridwen (equivalent to the Greek Demeter), was a sow goddess.
In Irish folklore, the dead were members of a separate Otherworld hostel or 'bruidhen'. Each one was ruled by a god, presiding over the supernatural feast. Pigs were slaughtered each day, eaten and magically reborn to be eaten again the next day.
The Brown Bull of Ulster, the centre-piece of the war between Connaught and Ulster, was thought to be a shape-changing swineherd who was the rival of another swine-herd. In order carry on their fight, the two swine-herds changed themselves into ravens, water-monsters, two rivers, two human champions, two eels, and finally into the Brown Bull of Ulster and the White-Horned Bull of Connaught.
According to the Welsh Mabinogian, pigs had been introduced to Britain as a result of trickery against King Pwyll, who was standing in as Lord of the Underworld for twelve months.
Minor goddesses, such as Arduinna (a cult in the Ardennes region of France) were seen as protectors of boars but also goddesses of hunting, allowing hunters of the right sort to be successful. The Romans later incorporated Arduinna into the cult of their goddess Diana.
Three Powerful Swineherds of Britain: in the Welsh triads, there were Three Powerful Swineherds of Britain, all with quasi magical powers.
Pryderi ap Pwyll (Pryderi the son of Pwyll). He guarded the pigs of Pendaran Dyfed in Glyn Cuch in Emlyn. Pryderi's father was the Pwyll who had introduced pigs to Britain.
Drystan, son of Tallwch, or Sir Tristram (of Tristram and Yseult fame) who guarded the pigs of March. Drystan was Sir Tristram, a Pictish Prince who served King March (or Mark) the King of Cornwall by driving out Irish invaders. Whilst guarding the pigs, he sent his swineherd to Essyellt or Isolde or Ysseult to arrange a meeting. This was the start of the Tristram and Isolde/Yseult romance, leading to marital discord, immorality, war, death and opera.
Coll, son of Collfewy. He guarded Henwen, the sow of Dallwyr Dallben. Henwen or Hen Wen, the sow, was the animal form of Cerridwen, the goddess of inspiration and keeper of a magic cauldron. When Henwen was about to bring forth her litter, she went to Penrhyn Awstin in Cornwall, where she entered the sea and swam to land at Aber Taroqi in Gwent is Coed. Henwen gave bounty to several areas in Wales, which, according to myth, enabled these regions to prosper.