Online Etymology Dictionary

Nereid: "sea-nymph," 1510s, from Greek Nereis (genitive Nereidos), daughter of the ancient sea-god Nereus, whose name is related to naros "flowing, liquid, I flow" (see naiad).
nerf: 1955, in nerf bars, hot-rodder slang for "custom bumpers;" from slang verb in auto racing (1953) meaning "to nudge something with a bumper in passing and knock it off course;" further etymology and signification unknown.

As a trademark name for toys made of foam-like material for indoor play, introduced 1970 (Nerf ball). By 1995 this had yielded a verbal sense of "to make less effective" (as a Nerf basketball is softer and lighter than the real thing).
neritic (adj.): 1891, from German neritisch (Haeckel, 1890), perhaps from Nerita, a genus of molluscs.
nertz (interj.): 1932, originally American English college slang, colloquial or euphemistic pronunciation of nuts as a slang retort of defiance or dismissal (1931).
nerve (n.): late 14c., nerf "sinew, tendon," from Old French nerf and directly from Medieval Latin nervus "nerve," from Latin nervus "sinew, tendon; cord, bowstring," metathesis of pre-Latin *neuros, from PIE *(s)neu- "tendon, sinew" (source also of Sanskrit snavan- "band, sinew," Armenian neard "sinew," Greek neuron "sinew, tendon," in Galen "nerve"). Sense of "fibers that convey impulses between the brain and the body" is from c. 1600.

Secondary senses developed from meaning "strength, vigor, energy" (c. 1600), from the "sinew" sense. Hence figurative sense of "feeling, courage," first attested c. 1600; that of "courage, boldness" is from 1809; bad sense "impudence, cheek" is from 1887. Latin nervus also had a figurative sense of "vigor, force, power, strength," as did Greek neuron. From the neurological sense come Nerves "condition of nervousness," attested from 1792; to get on someone's nerves, from 1895. War of nerves "psychological warfare" is from 1915.
nerve (v.): c. 1500, "to ornament with threads;" see nerve (n.). Meaning "to give strength or vigor" is from 1749. Related: Nerved; nerving.
nerve-racking (adj.): also nerveracking, 1812, from nerve + present participle of verbal sense of rack (n.1).
nerve-wracking (adj.): also nervewracking, 1867, from nerve + present participle of wrack (v.).
nervous (adj.): c. 1400, "affecting the sinews," from Latin nervosus "sinewy, vigorous," from nervus "sinew, nerve" (see nerve). Meaning "of or belonging to the nerves" in the modern sense is from 1660s. Meaning "suffering disorder of the nervous system" is from 1734; illogical sense "restless, agitated, lacking nerve" is 1740. Widespread popular use as a euphemism for mental forced the medical community to coin neurological to replace it in the older sense. Nervous wreck first attested 1862. Related: Nervously; nervousness.
nervy (adj.): "full of courage," 1870, from nerve + -y (2). Sense of "excitable" is from 1891.
nescience (n.): "ignorance," 1610s, from Late Latin nescientia, from nesciens (see nescient).
nescient (adj.): 1620s, from Latin nescientem (nominative nesciens) "ignorant, unaware," present participle of nescire "not to know, to be ignorant," from ne "not" + scire "to know" (see science).
nesh (adj.): "tender, delicate, weak," now a Northern England dialect word, from Old English hnesce "soft in texture" (cognate with early modern Dutch nesch, Gothic hnasqus), of unknown origin.
ness (n.): obsolete except in place names, Old English næs "a promontory," related to nasu "nose" (see nose (n.)). Cognate with Old Norse nes, Danish næs, Swedish näs, Middle Dutch nesse.
Nessie: colloquial name of the "Loch Ness monster," 1945. The loch is named for the river Ness, probably from an Old Celtic word meaning "roaring one."
nest (n.): Old English nest "bird's nest, snug retreat," also "young bird, brood," from Proto-Germanic *nistaz (source also of Middle Low German, Middle Dutch nest, German Nest), from PIE *nizdo- (source also of Sanskrit nidah "resting place, nest," Latin nidus "nest," Old Church Slavonic gnezdo, Old Irish net, Welsh nyth, Breton nez "nest"), probably from *ni "down" + *sed- (1) "to sit" (see sedentary).

Used since Middle English in reference to various accumulations of things (such as a nest of drawers, early 18c.). Nest egg "retirement savings" is from 1700, originally "a real or artificial egg left in a nest to induce the hen to go on laying there" (c. 1600).
nest (v.): Old English nistan "to build nests," from Proto-Germanic *nistijanan, from the source of nest (n.). The modern verb is perhaps a new formation in Middle English from the noun. Related: Nested; nesting.
nesting (adj.): 1650s, "making or using a nest," past participle adjective from nest (v.). Of objects, "fitted into one another," from 1934.
nestle (v.): Old English nestlian "build a nest," from nest (see nest (n.)) + suffix -el (3). Figurative sense of "settle (oneself) comfortably, snuggle" is first recorded 1540s. Related: Nestled; nestling.
nestling (n.): late 14c., "bird too young to leave the nest," from nest (n.) + diminutive suffix -ling.
Nestor: name for "old king renowned for wise counsel," 1580s, from Greek, name of the aged and wise hero in the "Iliad," king of Pylus, who outlived three generations. Klein says the name is literally "one who blesses," and is related to nostimos "blessed;" Watkins connects it with the root of the first element in nostalgia.
Nestorian (n.): in Church history (mid-15c.), a follower of Nestorius (Latinized form of Nestor), 5c. patriarch of Constantinople, whose doctrine attributed distinct divine and human persons to Christ and was condemned as heresy. As an adjective from 1560s. Related: Nestorianism.
net (n.): Old English net "netting, network, spider web, mesh used for capturing," also figuratively, "moral or mental snare or trap," from Proto-Germanic *natjan (source also of Old Saxon net, Old Norse, Dutch net, Swedish nät, Old High German nezzi, German Netz, Gothic nati "net"), originally "something knotted," from PIE *ned- "to twist, knot" (source also of Sanskrit nahyati "binds, ties," Latin nodus "knot," Old Irish nascim "I bind, oblige").
net (adj.): "remaining after deductions," 1510s, from earlier sense of "trim, elegant, clean, neat" (c. 1300), from Old French net "clean, pure," from Latin nitere "to shine, look bright, glitter" (see neat). Meaning influenced by Italian netto "remaining after deductions." As a noun, 1910.
net (v.1): "to capture in a net," early 15c., from net (n.). Related: Netted; netting.
net (v.2): "to gain as a net sum," 1758, from net (adj.). Related: Netted; netting.
nether (adj.): Old English niþera, neoþera "down, downwards, below, beneath," from Proto-Germanic *nitheraz (source also of Old Saxon nithar, Old Norse niðr, Old Frisian nither, Dutch neder, German nieder), from comparative of PIE *ni- "down, below" (source also of Sanskrit ni "down," nitaram "downward," Greek neiothen "from below," Old Church Slavonic nizŭ "low, down"). Has been replaced in most senses by lower (adj.).
Netherlands: from Dutch Nederland, literally "lower land" (see nether); said to have been used by the Austrians (who ruled much of the southern part of the Low Countries from 1713 to 1795), by way of contrast to the mountains they knew, but the name is older than this. The Netherlands formerly included Flanders and thus were equivalent geographically and etymologically to the Low Countries. Related: Netherlander; Netherlandish (c. 1600).
netherworld (n.): also nether-world, 1630s, "place beneath the earth," from nether + world.
netiquette (n.): 1993, coined punningly from net, short for Internet + etiquette.
netizen (n.): 1995, from net, short for Internet + citizen.
nettle (n.): stinging plant, Old English netele, from Proto-Germanic *natilon (source also of Old Saxon netila, Middle Dutch netele, Dutch netel, German Nessel, M.Da. nædlæ "nettle"), diminutive of *naton, perhaps from PIE root *ned- "to twist, knot" (see net (n.)). "[N]ettles or plants of closely related genera such as hemp were used as a source of fiber" [Watkins].
nettle (v.): c. 1400, "to beat with nettles," from nettle (n.). Figurative sense of "irritate, provoke" is from 1560s. Related: Nettled; nettling.
Nettled. Teized, provoked, out of temper. He or she has pissed on a nettle; said of one who is pevish or out of temper. [Grose, "Dictionary of the Vulgar Tongue," 1785]
nettled (adj.): "vexed, irritated," c. 1400, figurative adjectival use of past participle of nettle (v.).
nettlesome (adj.): 1766, from nettle (n.) + -some (1).
network (n.): "net-like arrangement of threads, wires, etc.," 1550s, from net (n.) + work (n.). Extended sense of "any complex, interlocking system" is from 1839 (originally in reference to transport by rivers, canals, and railways). Meaning "broadcasting system of multiple transmitters" is from 1914; sense of "interconnected group of people" is from 1947.
network (v.): 1887, "to cover with a network," from network (n.). From 1940 as "to broadcast over a (radio) network;" 1972 in reference to computers; 1980s in reference to persons. Related: Networked; networking.
Neufchatel: type of soft, white cheese, 1833, from Neufchâtel, small town in Normandy where it first was made.
neural (adj.): "pertaining to a nerve or nerves," 1830, from Greek neuron "nerve" (see neuro-) + adjectival suffix -al (1). Related: Neurally.
neuralgia (n.): 1807, from Greek neuron "nerve" (see neuro-) + -algia. Probably formed on model of French névralgie (1801). Related: Neuralgic.
neurasthenia (n.): "nervous exhaustion," 1854, medical Latin, from neur- (form of neuro- before a vowel) + asthenia "weakness" (see asthenia). Related: Neurasthenic.
neuritis (n.): "inflammation of a nerve or nerves," 1825, from Greek neuron "nerve" (see neuro-) + -itis "inflammation." Related: Neuritic.
neuro-: before vowels neur-, word-forming element meaning "pertaining to a nerve or nerves or the nervous system," from Greek neuro-, comb. form of neuron "nerve," originally "sinew, tendon, cord, bowstring," also "strength, vigor," from PIE *(s)neu- "tendon, sinew" (see nerve).
neuroglia (n.): 1867, medical Latin, coined 1853 by German pathologist Ludwig Karl Virchow (1821-1902) from neuro- + Late Greek glia "glue," from PIE *glei- "to stick together" (see clay).
neurologist (n.): 1801, from neurology + -ist.
neurology (n.): "scientific study of the nervous system," 1680s, from Modern Latin neurologia, from Modern Greek neurologia (1660s), from neuro- (see neuro-) + -logia "study" (see -logy). Related: Neurological.
neuron (n.): "a nerve cell with appendages," 1891, from German Neuron, from Greek neuron (see neuro-). Used earlier (1884) for "the spinal cord and brain."
neuropathy (n.): 1827, from neuro- + -pathy. Related: Neuropath; neuropathic; neuropathist.
neuroscience (n.): 1963, from neuro- + science.
neurosis (n.): 1776, "functional derangement arising from disorders of the nervous system," coined by Scottish physician William Cullen (1710-1790) from Greek neuron "nerve" (see neuro-) + Modern Latin -osis "abnormal condition." Used in a general psychological sense since 1871; clinical use in psychiatry dates from 1923.