Are yams and sweet potatoes the same?
c.1300, nygromauncy, "divination by communication with the dead," from Old French nigromancie "magic, necromancy, witchcraft, sorcery," from Medieval Latin nigromantia (13c.), from Latin necromantia "divination from an exhumed corpse," from Greek nekromanteia, from nekros "dead body" (see necro-) + manteia "divination, oracle," from manteuesthai "to prophesy," from mantis "prophet" (see mania). Spelling influenced in Medieval Latin by niger "black," on notion of "black arts." Modern spelling is a mid-16c. correction. Related: Necromantic.
communication with the dead, usually in order to obtain insight into the future or to accomplish some otherwise impossible task. Such activity was current in ancient times among the Assyrians, Babylonians, Egyptians, Greeks, Romans, and Etruscans; in medieval Europe it came to be associated with black (i.e., harmful, or antisocial) magic and was condemned by the church