1824, originally in African-American vernacular in the South.
The slaves themselves entertain the very highest contempt for white servants, whom they designate as 'poor white trash.' [Fanny Kemble, journal, Jan. 6, 1833]
[T]he term [poor white] is rather loosely applied by Northern writers even to mountaineers and to small farmers who live on a precarious footing. But in the Southern conception, not everyone who is both poor and white is a "poor white." To the Southerner, the "poor white" in the strictest sense is a being beyond the pale of even the most generous democratic recognition; in the negro's term, "po' white trash," or so much social débris. [Robert Penn Warren, "The Briar Patch," 1930, footnote]
c. 1200, "lacking money or resources, destitute of wealth; needy, indigent;" also "small, scanty," also voluntarily and deliberately, "devoid of possessions in conformity with Christian virtues," from Old French povre "poor, wretched, dispossessed; inadequate; weak, thin" (Modern French pauvre), from Latin pauper "poor, not wealthy," from pre-Latin *pau-paros "producing little; getting little," a compound from the roots of paucus "little" (from PIE root *pau- (1) "few, little") and parare "to produce, bring forth" (from PIE root *pere- (1) "to produce, procure").
It replaced Old English earm (from Proto-Germanic *arma-, which is of disputed origin). Late 13c. as "unfortunate, to be pitied or regretted." In contemptuous use, "morally inferior, miserable, wretched," by early 15c. Used figuratively ("spiritually poor") from early 14c. (to be poor in spirit is to be "spiritually humble"). Meaning "deficient in desirable or essential qualities" is from c. 1300. In reference to inhabited places from c. 1300; of soil, etc., from late 14c. In modest or apologetic use, "humble, slight, insignificant," from early 15c.
The poor boy sandwich, made of simple but filling ingredients, was invented and named in New Orleans in 1921. To poor mouth "deny one's advantages" is from 1965 (to make a poor mouth "whine" is Scottish dialect from 1822). Slang poor man's________ "the cheaper alternative to _______," is from 1854. Poor relation "relative or kinsman in humble circumstances" is by 1720.
"to discard as worthless," 1859, from trash (n.); in the sense of "destroy, vandalize" it is attested from 1970; extended to "criticize severely" in 1975. Related: Trashed; trashing.
late 14c., "thing of little use or value, waste, refuse, dross," perhaps from a Scandinavian source (compare Old Norse tros "rubbish, fallen leaves and twigs," Norwegian dialectal trask "lumber, trash, baggage," Swedish trasa "rags, tatters"), of unknown origin. Applied to ill-bred persons or groups from 1604 ("Othello"), and especially of poor whites in the U.S. South by 1831. Applied to domestic refuse or garbage from 1906 (American English). Trash-can is attested from 1914. To trash-talk someone or something is by 1989.
"poor persons collectively," mid-12c., from poor (adj.). The Latin adjective pauper "poor" also was used in a noun sense "a poor man." Middle English used poorlet (late 14c.) "poor man, wretched person" to translate Latin paupercula in the Bible.
Old English hwit "bright, radiant; clear, fair," also as a noun (see separate entry), from Proto-Germanic *hweit- (source also of Old Saxon and Old Frisian hwit, Old Norse hvitr, Dutch wit, Old High German hwiz, German weiß, Gothic hveits), from PIE *kweid-o-, suffixed form of root *kweit- "white; to shine" (source also of Sanskrit svetah "white;" Old Church Slavonic sviteti "to shine," svetu "light;" Lithuanian šviesti "to shine," švaityti "to brighten").
As a surname, originally with reference to fair hair or complexion, it is one of the oldest in English, being well-established before the Conquest. Meaning "morally pure" was in Old English. Association with royalist causes is late 18c. Slang sense of "honorable, fair" is 1877, American English; in Middle English it meant "gracious, friendly, favorable." The racial sense "of those races (chiefly European or of European extraction) characterized by light complexion" is recorded from c. 1600; meaning "characteristic of or pertaining to white people" is from 1852, American English. White supremacy attested from 1868, American English [John H. Van Evrie, M.D., "White Supremacy and Negro Subordination," New York, 1868]; white flight is from 1966, American English.
White way "brightly illuminated street in a big city" is from 1908. White flag of truce or surrender is from c. 1600. White lie is attested from 1741. White Christmas is attested from 1847. White House as the name of the U.S. presidential residence is recorded from 1811. White water "river rapids" is recorded from 1580s. White Russian "language of Byelorussia" is recorded from 1850; the mixed drink is from c. 1978. Astronomical white dwarf is from 1924. White witch, one who used the power for good, is from 1620s.
Old English hwit "whiteness, white food, white of an egg," from white (adj.). Also in late Old English "a highly luminous color devoid of chroma." Meaning "white part of the eyeball" is from c. 1400. Meaning "white man, person of a race distinguished by light complexion" is from 1670s; white man in this sense is from 1690s. White man's burden is from Kipling's 1899 poem:
Take up the White Man's burden—
The savage wars of peace—
Fill full the mouth of Famine
And bid the sickness cease;
And when your goal is nearest
The end for others sought,
Watch sloth and heathen Folly
Bring all your hopes to nought.