In Jewish folklore, a dybbuk (or dibbuk) is the spirit or soul of a dead person that enters a living body and takes possession of it. Dybbuk is a Hebrew word meaning "attachment." According to tradition, the dybbuk is a restless spirit that must wander about—because of its sinful behavior in its previous life—until it can "attach" itself to another person. The dybbuk remains within this person until driven away by a religious ceremony.
Belief in such spirits was common in eastern Europe during the 1500s and 1600s. Sometimes people who had nervous or mental disorders were assumed to be possessed by a dybbuk. Often a special rabbi was called to exorcise, or drive out, the evil spirit.
Shloime Ansky wrote a play in Yiddish called The Dybbuk in 1916. It concerns a rabbinical student named Khonnon who calls upon Satan to help him win Leye, the woman he loves. When Khonnon dies, he becomes a dybbuk and takes possession of Leye. After she is freed of the spirit, Leye dies, and her spirit joins that of Khonnon.