The Celtic pantheon, as it comes to us today, is nowhere near as well preserved as that of Greece and Rome. Some Gods are archetypes, expressing a feeling or attitude: love, war, mothering, growth, inspiration.
When the Romans came to our lands, they equated many of our deity with their own and, whilst this has given us an understanding of the energy behind the names, it has coloured our vision of the gods with a Roman hue.
Later influences from Viking settlement also become part of our language. Many of town names are Viking and four of our weekdays still venerate the Viking Gods: Tew, Woden, Thor, and Freya replacing the Roman Gods of Mars, Mercury, Jupiter and Venus, leaving only Saturn, Sun and Moon as a reminder of the influence of the Roman planetary deity.
The story of Celtic deity is told in the Mabinogion, the verses of Taliessin, and early manuscripts where the tradition of oration was finally captured in writing; firstly, by Roman invaders and then by Christian scribes. But they were heard by the untrained ear with little understanding of the sub-text and by those who, no doubt, added a veneer from their own values.
Nonetheless, it is possible to see the archetypes in the Children of Dôn: the trickster God, Gwidion; the mother/teacher Goddess, Arianrhod.