Here is what I learned from reading Gay Magick about the origins of the winter solstice celebration, and those who are more knowledgeable, please make corrections and additions.
The winter solstice celebration is called the Yule, an ancient word meaning wheel. It refers to the cycle of life, and the ancients explained it this way. On the winter solstice, the Goddess gives birth to the sun, and from then on until midsummer, the sun grows stronger each day. At midsummer, the sun becomes her lover and the forces of dark and light are at equal strength. Then, at the fall harvest, the sun is cut down or "reaped" and begins growing weaker as the dark, watery feminine elements grow stronger. The whole process is repeated in the cycle of the seasons each year. This story was co-opted by the Greeks in the story of Hades and Persephone and by the early Christians in the story of Jesus. When they adopted the story, the Christians made the feminine role in this cycle taboo.
