c. 1300, from Old French veine "vein, artery, pulse" (12c.), from Latin vena "a blood vessel," also "a water course, a vein of metal, a person's natural ability or interest," of unknown origin. The mining sense is attested in English from late 14c. (Greek phleps "vein" had the same secondary sense). Figurative sense of "strain or intermixture" (of some quality) is recorded from 1560s; that of "a humor or mood, natural tendency" is first recorded 1570s.
"arrangement of veins," 1640s, of plant structures, noun of state from Latin vena "vein" (see vein). Related: Venational.
plural of varix "dilated vein" (c. 1400), from Latin varix "a varicose vein," which de Vaan derives from varus "bent outward, bow-legged," which is of uncertain origin (see vary).
"important vein of an ore or mineral in rock," 1849, from mother (n.1) + lode (n.); said to be a translation of Mexican Spanish veta madre, a name given to rich silver veins. The American use is first in reference to a conspicuous vein of quartz rich in gold discovered during the gold rush in the Sierra Nevada of California. The colloquial or figurative sense of "richest source of something" is by 1916.
also main-line, "inject (drugs) intravenously," 1934, from main line in American English slang sense "principal vein into which drugs can be injected" (1933).