"offensive to the senses, fetid or soured by chemical change, having a tainted small or taste," 1640s, from Latin rancidus "rank, stinking, offensive" (also source of Italian rancido, Spanish rancio), from rancere "be spoiled or rotten," a word of unknown origin. Compare rancor. German ranzig is from French rancide. Related: Rancidness; rancidity.
c. 1200, rancour, "a nourished envy; bitterness, hatred, malice," from Old French rancor "bitterness, resentment; grief, affliction," from Late Latin rancorem (nominative rancor) "rancidness, a stinking smell" (Palladius); "grudge, bitterness" (Hieronymus and in Late Latin), from Latin rancere "to stink," a word of unknown etymology (compare rancid). Sometimes in 15c. medical works the word is used in English in its literal Latin sense.
word-forming element in science indicating "rotten, putrid, decaying," from Greek sapros "rotting, rotten, rancid," also, of wine, "matured," which is related to sēpein "to rot," a word of unknown origin.
originally of texture, "hairy," 1530s, probably from Middle English harske "rough, coarse, sour" (c. 1300), a northern word of Scandinavian origin (compare Danish and Norwegian harsk "rancid, rank"), related to Middle Low German harsch "rough, raw," German harst "a rake;" perhaps from PIE root *kars- "to scrape, scratch, rub, card" (source also of Lithuanian karšiu, karšti "to comb," Old Church Slavonic krasta, Russian korosta "scab," Latin carduus "thistle," Sanskrit kasati "rubs, scratches"). Meaning "offensive to feelings" is from 1570s; that of "disagreeable, rude" from 1610s.
Old English ranc "proud, overbearing, haughty, showy," senses now obsolete, from Proto-Germanic *rankaz (source also of Danish rank "right, upright," German rank "slender," Old Norse rakkr "straight, erect"), which is of uncertain origin, possibly related to Old Norse and Old English rinc "man, warrior." Related: Rankly; rankness.
In reference to plant growth, "vigorous, luxuriant, abundant, copious" (also figurative) it is recorded from c. 1300. The sense also evolved in Middle English to "large and coarse" (c. 1300), then to "corrupt, loathsome, foul" (mid-14c.), perhaps via the notion of "excessive and unpleasant," perhaps also influenced in this by French rance "rancid." Specifically as "having an offensive, strong smell" by 1520s. In Middle English also "brave, stout-hearted; splendid, admirable." In 17c. it also could mean "lewd, lustful."
The development of the word in Eng. is, however, far from clear, as the OE. uses are not quite the primitive ones. In ME. also it chiefly occurs in alliterative verse, app. more for convenience than to express definite meanings. In the later language the chief difficulty is to decide which of the more original senses are represented in the transferred uses. [OED]
Much used 16c. as a pejorative intensive (as in rank folly). This is possibly the source of the verb meanings "to reveal another's guilt" (1929, underworld slang) and that of "to harass, insult, abuse," 1934, African-American vernacular, though this also may be so called from the role of the activity in establishing social hierarchy (and thus from rank (n.)).