A witch is a monster sucking the life, blood, milk, or other liquid from farm, home, or the community (well, rain, etc.). She can shape-shift, discard her skin, and may be in league with nefarious entities like Satan.
It has been recognized that witches are some part projection and some part social pariah and target. Typical women marked as witches were herbalists, midwives, and borderland crones. With the advent of moral panics such as the European Witch Craze, such women were tortured and killed in abominable ways, and their possessions redistributed. Their status, as victims of a mad mob, was as heretic before the fires of purification.
Later, religious witchcraft was invented, and witches became known as nature worshippers, goddess worshippers, worshippers of the Great Goddess, and occultists, spellcasters, and feminist religious.