Celtic folklore dates witches at Halloween back to the pagan goddess known as "the crone" (also "the old one" or "Earth mother") who was honored during Samhain and symbolized wisdom and the changing of the season.
The Celtics believed that when someone died, his or her soul went to the crone's cauldron, known as the Earth mother's womb, to await reincarnation. The crone stirred the cauldron to allow new spirits in and old spirits to be reborn.
Witches also became known as "evil" by the Christian faith, who believed talented and intelligent women were receiving their knowledge and power from something other than God. Accusing women of witchcraft was used as a way to keep them from threatening male supremacy. Witches in Christian folklore were ugly because evil was ugly, and typical symbols of witchcraft (brooms, cauldrons, and cats) were associated with the home and women's work.
More: What is Witchcraft?