necromancy (n.)

late 14c., "mental derangement characterized by excitement and delusion," from Late Latin mania "insanity, madness," from Greek mania "madness, frenzy; enthusiasm, inspired frenzy; mad passion, fury," related to mainesthai "to rage, go mad," mantis "seer," menos "passion, spirit," all of uncertain origin, perhaps from PIE *mnyo-, suffixed form of root *men- (1) "to think," with derivatives referring to qualities and states of mind or thought.

Mania is manifested by psychic elevation, increased motor activity, rapid speech and the quick flight of ideas. [Scientific American, September 1973]

Sense of "fad, craze, enthusiasm resembling mania, eager or uncontrollable desire" is by 1680s, from French manie in this sense. Sometimes nativized in Middle English as manye. Used since 1500s as the second element in compounds expressing particular types of madness (such as nymphomania, 1775; kleptomania, 1830; megalomania, 1890), originally in Medical Latin, in imitation of Greek, which had a few such compounds, mostly post-classical: gynaikomania (women), hippomania (horses), etc.

late 14c., nygromanser, nigromauncere, "sorcerer, adept in black magic," from Old French nigromansere, from nigromancie (see necromancy). Properly "one who communicates with the dead" but typically used in a broader sense in English.

Proto-Indo-European root meaning "death." It forms all or part of: innocent; innocuous; internecine; necro-; necropolis; necrosis; necromancy; nectar; nectarine; nociceptive; nocuous; noxious; nuisance; obnoxious; pernicious.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit nasyati "disappears, perishes," Avestan nasyeiti "disappears," nasu- "corpse," Old Persian vi-nathayatiy "he injures;" Greek nekros "corpse;" Latin nex, genitive necis "violent death, murder" (as opposed to mors), nocere "to harm, hurt," noxius "harmful;" Greek nekus "dead" (adj.), nekros "dead body, corpse;" Old Irish ec, Breton ankou, Welsh angeu "death."