necromancyyoudaoicibaDictYouDict[necromancy 词源字典]
necromancy: [13] Greek nekrós meant ‘corpse’ (it has given English necrophilia [19], necropolis ‘cemetery’ [19], and necrosis ‘death of tissue’ [17] as well as necromancy, and goes back to a base *nek- ‘kill’ which also produced Latin nex ‘killing’, source of English internecine and pernicious, and possibly Greek néktar, source of English nectar).

Addition of manteíā ‘divination’, a derivative of mántis ‘prophet, diviner’ (from which English gets the insectname mantis [17], an allusion to its raised front legs, which give it an appearance of praying), produced nekromanteíā ‘foretelling the future by talking to the dead’, which passed into late Latin as necromantīa. By the Middle Ages the application of the term had broadened out to ‘black magic’ in general, and this led to an association of the first element of the word with Latin niger ‘black’.

Hence when it first arrived in English it was in the form nigromancy, and the restoration of the original necro- did not happen until the 16th century.
=> internecine, mantis, pernicious[necromancy etymology, necromancy origin, 英语词源]
necromancy (n.)youdaoicibaDictYouDict
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.