A very offensive term meaning "To bring the price of (something) down," referring to the stereotype that Jewish people are massive cheapskates. If you use this phrase in front of a Jewish person, expect to be punched in the face.
Sometimes Jewitches are Jews who have become Wiccan. Sometimes Jewitches are Jews who practice an earth-based and mystical form of the religion. It is a broad umbrella-term for a wide range of spiritual practice.