Ireland's OWN: Celtic Symbols

The Dog

Sacred to the faeries, dogs were held in high regard by the Tuatha de Danaan.
Many Celtic myths involve dogs or dog familiars, which belonged to heroic figures or deities, and wars were often fought for and over them.
Dormarth, a dog, was the gatekeeper to the Afterworld.
Irish Celts maintained that true curses could be cast with the aid of a dog.
In Celtic traditions, dogs are also associated with healing.
Dogs figure prominently in the legends of Fin MacCumhaíl
and Cú Chulainn.
Cu Chulainn was named Sétanta until he killed the hound of Culann the smith, after which he was known as Cú Chulainn — Culann's Hound
Dogs are also the archetypal symbols of shapeshifters.
In Wales, the banging of utensils on New Year's Eve was done to drive off Cwn Annwn, the phantom black dogs of the underworld that pass through the air on New Year's eve.

Sources include: Personal knowledge, Celtic Magic by DJ Conway, The Secret Language of Symbols by David Fontana, The Celtic Book of the Dead by Caitlin Matthews, Celtic Wisdom by Caitlin and John Matthews, Celtic Cross Stitch by Anne Orr and Lesley Clark, The Pagan Book of Days by Nigel Pennick, and Celtic Myth and Magick by Edain McCoy