"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.
mid-14c., "the customary and unwritten laws of England as embodied in commentaries and old cases" (see common (adj.)), as opposed to statute law. Phrase common-law marriage is attested from 1909.
in reference to a kind of loose, full gown worn by women, 1878, from Old Mother Hubbard, nursery rhyme, which was printed 1805, written by Sarah Catherine Martin (1768-1826) but based on earlier material of unknown origin. The name is attested from 1591.
named for 17c. Irish-born chemist and physicist Robert Boyle, who published it in 1662.