nigra n., adj.

1550s, "member of a black-skinned race of Africa," from Spanish or Portuguese negro "black," from Latin nigrum (nominative niger) "black, dark, sable, dusky" (applied to the night sky, a storm, the complexion), figuratively "gloomy, unlucky, bad, wicked," according to de Vaan a word of unknown etymology; according to Watkins, perhaps from PIE *nekw-t- "night." The Latin word also was applied to the black peoples of Africa, but the usual terms were Aethiops and Afer.

As an adjective from 1590s. Use with a capital N- became general early 20c. (e.g. 1930 in "New York Times" stylebook) in reference to U.S. citizens of African descent, but because of its perceived association with white-imposed attitudes and roles the word was ousted late 1960s in this sense by Black (q.v.).

Professor Booker T. Washington, being politely interrogated ... as to whether negroes ought to be called 'negroes' or 'members of the colored race' has replied that it has long been his own practice to write and speak of members of his race as negroes, and when using the term 'negro' as a race designation to employ the capital 'N' [Harper's Weekly, June 2, 1906]

Meaning "African-American vernacular, the English language as spoken by U.S. blacks" is from 1704. French nègre is a 16c. borrowing from Spanish negro. Older English words were Moor and blackamoor. A Middle English word for "Ethiopian" (perhaps also "a negro" generally) was blewman "blue man."

1786, earlier neger (1568, Scottish and northern England dialect), negar, negur, from French nègre, from Spanish negro (see Negro). From the earliest usage it was "the term that carries with it all the obloquy and contempt and rejection which whites have inflicted on blacks" [cited in Gowers, 1965, probably Harold R. Isaacs]. But as black African inferiority was at one time a near universal assumption in English-speaking lands, the word in some cases could be used without deliberate insult. More sympathetic writers late 18c. and early 19c. seem to have used black (n.) and, after the American Civil War, colored person.

Nigger is more English in form than negro, and was formerly and to some extent still is used without intent; but its use is now confined to colloquial or illiterate speech, in which it generally conveys more or less of contempt. [Century Dictionary, 1895]

"You're a fool nigger, and the worst day's work Pa ever did was to buy you," said Scarlett slowly. ... There, she thought, I've said "nigger" and Mother wouldn't like that at all. [Margaret Mitchell, "Gone With the Wind," 1936]

It was also applied by English colonists to the dark-skinned native peoples in India, Australia, Polynesia.

One hears the contemptuous term "nigger" still applied to natives by those who should know better, especially by youths just come from home, and somewhat intoxicated by sudden power. [Samuel Smith, "India Revisited," in "The Contemporary Review," July 1886]

 The reclamation of the word as a neutral or positive term in black culture (not universally regarded as a worthwhile enterprise), often with a suggestion of "soul" or "style," is attested first in the U.S. South, later (1968) in the Northern, urban-based Black Power movement. The variant nigga, attested from 1827 (as niggah from 1835), is found usually in situations where blacks use the word. Also compare nigra.

[F]or when a town black has called a country black (equally black with himself) a "dam black plantation nigga," you may know that he has been terribly provoked, and has now ejected his last drop of gall in that most contemptuous epithet. [The Pamphleteer, vol. XXVIII, No. LVI, 1827]

Used in combinations (such as nigger-brown) since 1840s for various dark brown or black hues or objects; euphemistic substitutions (such as Zulu) began to appear in these senses c. 1917. Brazil nuts were called nigger toes by 1896. Nigger stick "prison guard's baton" is attested by 1971. To work like a nigger "work very hard" is by 1836.

Slang phrase nigger in the woodpile "a concealed motive or unknown factor affecting a situation in an adverse way" [OED] is attested by 1800; Thornton's "American Glossary" (1912) defines it as "A mode of accounting for the disappearance of fuel," hence "an unsolved mystery." Nigger heaven "the top gallery in a (segregated) theater" first attested 1878 in reference to Troy, N.Y. Nigger-shooter "slingshot" is by 1876.