"consisting of or resembling nacre," 1807, from nacre + -ous.

slang for "nothing," 1933 (Hemingway), from Spanish nada "nothing," from Latin (res) nata "small, insignificant thing," literally "(thing) born," from natus, past participle of nasci "to be born" (Old Latin gnasci), from PIE root *gene- "give birth, beget."

First in Hemingway's "A Clean, Well-Lighted Place," set in a Spanish cafe, in which the word figures largely:

What did he fear? It was not fear or dread. It was nothing that he knew too well. It was all a nothing and a man was nothing too. It was only that and light was all it needed and a certain cleanness and order. Some lived it and never felt it but he knew it all was nada y pues nada y nada y pues nada. Our nada who art in nada, nada be thy name thy kingdom nada thy will be nada in nada as it is in nada. Give us this nada our daily nada and nada us our nada as we nada our nadas and nada us not into nada but deliver us from nada; pues nada. Hail nothing full of nothing, nothing is with thee.

the earlier form of adder (q.v.). Also see N.

"Public agitation for greater safety and higher quality in consumer goods" [OED], 1969, in reference to the concerns and methods of U.S. lawyer and consumer advocate Ralph Nader (b. 1934) + -ism.

late 14c., in astronomy, "imaginary point of the celestial sphere vertically opposite to the zenith of the sun; the inferior pole of the horizon," from Medieval Latin nadir, from Arabic nazir "opposite to," in nazir as-samt, literally "opposite direction," from nazir "opposite" + as-samt "road, path" (see zenith). Transferred sense of "lowest point" of anything is recorded by 1793.

"spot or blemish on the skin," 1610s, from Latin naevus "mole, birthmark, wart," from *gnaevus "birthmark," literally "born in," from PIE root *gene- "to give birth, beget," with derivatives referring to aspects and results of procreation. Now obsolete; the Latin form has been used since c. 1835 in anatomy and zoology.

British slang word with varied senses, not all of them certainly connected; see Partridge, who lists two noun uses: "female pudenda" (c. 1845), which might be back-slang from fan, shortening of fanny (in the British sense); and "nothing," in prostitutes' slang from c. 1940; a verbal use, a euphemism for fuck (v.) in oaths, imprecations, expletives (as in naff off), 1959, "making it slightly less obvious than eff" [Partridge]; and an adjective naff "vulgar, common, despicable," which is said to have been used in 1960s British gay slang for "unlovely" and thence adopted into the jargons of the theater and the armed forces.