In Judaic culture, ob (or owb) is the word which refers to either the spirit of a dead human, the medium possessed by the dead person’s spirit (derived from “skin-bottle” or “leather bottle”, referring to the person as a vessel, which is usually the conjurer themselves), the artifacts used to conjure such spirits, or even the necromancer themselves. The practice of necromancy was relatively common among pagan Jewish belief based on the prohibitions of it and other such divination practices mentioned in the Old Testament. References to such wizards and familiar spirits can be found in the Books of Leviticus and Deuteronomy.
The Hebrew ob has cognates in various Mesopotamian languages, where it means “deceased person’s spirit” and “pit” (referring originally to the pit from which the spirit of a dead person, usually an ancestor, could be summoned, but later to any hole in the ground). It should be noted the equivalent word to ob in Greek, pytho, also refers to both the conjurer and the spirit possessing them.