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.
Old English heap "pile (of things); great number, crowd, multitude (of persons)," from West Germanic *haupaz (source also of Old Saxon hop, Old Frisian hap, Middle Low German hupe, Dutch hoop, German Haufe "heap"), of uncertain origin. The group is perhaps related to Old English heah "high" (see high), but OED suggests a common origin with Latin cubare "lie down," and Boutkan says it is probably not Indo-European at all.
Slang meaning "old car" is attested from 1924. Earlier it meant "slovenly woman" (1806). As a characteristic word in American Indian English speech, "a lot, a great deal," by 1832.
One grain of sand does not make a heap. A second grain of sand added to the first does not make a heap. Indeed each and every grain of sand, when added to the others, does not make a heap which was not a heap before. Therefore, all the grains of sand in existence can still not a heap make. [the fallacy of the heap, as described in Malcolm Murray and Nebojsa Kujundzic, "Critical Reflection," 2005]
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]
"place where refuse is dumped, pile or heap of refuse matter," 1865, originally of mining operations, from dump (v.). In reference to sites for discarding domestic trash by 1872. Dumping-ground is by 1857. Meaning "any shabby place" is from 1899. Military sense of "collection of ammunition, equipment, etc. deposited in a convenient place for later use" is by 1915. Meaning "act of defecating" is from 1942. Dump-truck is from 1930.