Английский Этимологический словарь - need (n.)

- O.E. nied (W.Saxon), ned (Mercian) "necessity, compulsion, duty," from P.Gmc. *nauthis, from PIE *nau- "death, to be exhausted." The more common O.E. word for "need, necessity, want" was рearf, but they were connected via a notion of "trouble, pain," and the two formed a compound, niedрearf "need, necessity, compulsion, thing needed." Nied also may have been infl. by O.E. neod "desire, longing," which was often spelled the same. Common in O.E. compounds, e.g. niedfaru "compulsory journey," a euphemism for "death;" niedhжmed "rape," the second element being an O.E. word meaning "sexual intercourse;" niedling "slave." The verb is O.E. neodian "be necessary," from the noun. Needs is O.E. nede, instr. and gen. sing. of nied; Needy is M.E. nede. Phrase the needful "money" is attested from 1774. In archaic construction needs must, needs is an adverb reinforcing must, hence the genitive ending.