non-metallic element occurring naturally as diamond, graphite, or charcoal, 1789, coined 1787 in French by Lavoisier as charbone, from Latin carbonem (nominative carbo) "a coal, glowing coal; charcoal," from PIE root *ker- (3) "heat, fire."
Carbon 14, long-lived radioactive isotope used in dating organic deposits, is from 1936. Carbon-dating (using carbon 14) is recorded from 1958. Carbon cycle is attested from 1912; carbon footprint was in use by 2001. Carbon-paper "paper faced with carbon, used between two sheets for reproduction on the lower of what is drawn or written on the upper" is from 1855, earlier it was carbonic paper (1850).
"very hard mineral" (crystalline aluminum oxide) used for grinding and polishing other gems, steel, etc., 1728, from Anglo-Indian, from Tamil (Dravidian) kurundam "ruby sapphire" (Sanskrit kuruvinda), which is of unknown origin. It is a dull or opaque variety of sapphire, amethyst, ruby, and topaz; in hardness it is next to diamond.
1530s, "born out of wedlock," formed in English (and replacing earlier illegitime, c. 1500), modeled on Late Latin illegitimus "not legitimate" (see il- + legitimate). Sense of "unauthorized, unwarranted" is from 1640s. Phrase illegitimi non carborundum, usually "translated" as "don't let the bastards grind you down," is fake Latin (by 1965, said to date from c. 1939). Carborundum was a brand of abrasives. Related: Illegitimately.