The only free and comprehensive online etymological dictionary of the Spanish language
naturaleza f. (Noun) "nature"

Early 13th cent. From natural and -eza, an abstract noun-forming suffix.
nave f. (Noun) "ship"

In 10th cent. derivation naveta. First direct attestation is 12th cent. From Latin navis 'id.' From Proto-Italic *nāw- 'id.' From Proto-Indo-European *neh2-u̯- 'id.' From the root *neh2- "to swim" (see nadar).

Romance: Western Vulgar Latin: Asturian nave, Portuguese nave, Galician nave, Catalan nau, French nef, Italian nave ; Eastern Vulgar Latin: Aromanian nai, Romanian naie ; Sardinian: nae

Indo-European: Celtic: Old Irish náu "ship," Middle Welsh noe "bowl," Middle Breton neau "vase;" Germanic: Old Norse nór "ship," Norwegian no "wooden bowl," Old English nōwend "skipper;" Hellenic: Ancient Greek ναῦς (naûs) "ship;" Armenian: naw "boat;" Indo-Iranian: Sanskrit náu- "ship," Young Avestan nāuu(a)iia- "crossable by ship"
navidad f. (Noun) "Christmas"

Early 13th cent. Old Spanish nadvidad, from natividad. From Latin nativus "born," from nascor "to be born" (see nacer) and -ivus (see -ivo).

Romance: Western Vulgar Latin: French naïf, natif, Italian nativo ; Eastern Vulgar Latin: Romanian nativ
necesario (Adjective) "necessary"

13th cent. From Latin necessarius 'id.,' formed from necesse "necessary" and -arius, an adjective-forming suffix (see -ario). Necesse derives from ne- "not" and cesse "avoiding." Hypothetically, cesse is from *ced-tis "avoidable," with the first element is from the verb cedere "to withdraw" (see ceder). While every linguist connects cesse with cedere in some way, the precise path the word took is unclear (see de Vann (2014) for further discussion).

Romance: Western Vulgar Latin: French nécessaire, Italian necessario
necesitar (Verb) "to need;" "to necessitate"

17th cent. From Medieval Latin necessitare 'id.,' a verb formed from Latin necessitas "necessity," from necesse "necessary" (see necesario for further etymology of necesse) and -itas, a noun-forming suffix indicating a state of being (see -edad).

Nesitar, colloquial in Aragon and Latin America, probably dates back to a Medieval haplology.

Romance: Western Vulgar Latin: French nécessité, Italian necessità
negociar (Verb) "to negotiate"

Late 15th cent. From Latin negotiare 'id.' From negotium "business" (see negocio).

Romance: Western Vulgar Latin: Portuguese negociar, Catalan negociar, French négocier, Italian negoziare ; Eastern Vulgar Latin: Romanian neguța
negocio m. (Noun) "business"

13th cent. From Latin negotium 'id.,' a compound of nec "not" (see ni) and otium "leisure" (see ocio).

Romance: Western Vulgar Latin: Asturian negociu, Portuguese negócio, Catalan negoci, French négoce, Italian negozio ; Eastern Vulgar Latin: Romanian negoț

"The Latin negōtium... has a peculiar history:

"A calque on Gr. a-skholía, neg-ōtium conveys the same senses as the Greek model, which are positive despite the negative formation: “occupation, impediment, difficulty.”

"At a later stage negōtium is the equivalent of Gr. prâgma ‘a thing’, but also more specifically and especially in derivations “commercial affairs.” A calque, semantically this time, on prâgma , negōtium becomes the designation for “business.”" ~ E. Benveniste, Indo-European Language and Society (1973)
negro (1) (Noun) "black (person)"

From Latin nigrum, accusative of niger "black (person)" but the sense of niger as an abstract color is first (see negro (2)).

As a surname, it follows a tradition dating to Roman times; given to people black or dark of skin.

Romance: Western Vulgar Latin: Asturian negru, Portuguese negro, Galician negro, Catalan negre, French nègre, Italian negro ; Eastern Vulgar Latin: Aromanian negru, Romanian negru ; Sardinian: négru
negro (2) (Adjective, Noun) "black"

12th cent. From Latin nigrum, accusative of niger 'id.' Of unknown origin. Possibly related to Tocharian B ñakre "darkness." If so, an ancestral word *ni̯g(h)-ro- or *ni̯ǵ(h)-ro- 'id.' is reconstructed in Proto-Indo-European by Isebaert (1977).

As a surname, it was given to people with black hair or beards, but see also negro (1).

Romance: Western Vulgar Latin: Asturian negru, Portuguese negro, Galician negro, Catalan negre, French nègre, Italian negro ; Eastern Vulgar Latin: Aromanian negru, Romanian negru ; Sardinian: négru
nene (Noun) "child;" (slang) "cutey"

18th cent. Of unknown origin. Probably related to niño and probably by way of reduplication of the first syllable *ne- during the late Vulgar Latin period. A time when <i> and <e> were markedly unstable in Iberia when representing short vowels.

Dialect Variants: Colunga nenín, nenucu, nenón.