Etymology
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common law (n.)

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.

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common sense (n.)

late 14c., originally an internal mental power supposed to unite (reduce to a common perception) the impressions conveyed by the five physical senses (Latin sensus communis, Greek koine aisthesis). Thus "ordinary understanding, without which one is foolish or insane" (1530s); the meaning "good sense" is from 1726. Also, as an adjective, common-sense "characterized by common sense" (1854).

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coulda 

in writing, to indicate the common casual pronunciation of could have, by 1909.

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rank and file (n.)

1590s, in reference to the horizontal and vertical lines of soldiers marching in formation, from rank (n.) in the military sense of "number of soldiers drawn up in a line abreast" (1570s) + file (n.1). Thence generalized to "common soldiers" (1796) and "common people, general body" of any group (1860).

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sub voce 
Latin, literally "under the word or heading." A common dictionary reference, usually abbreviated s.v.
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sandpiper (n.)

common name of a small wading bird that runs along the sand and utters a piping note, 1670s, from sand (n.) + piper.

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dusty miller (n.)
common name for auricula, 1825, so called from the powder on the leaves and flower; millers, by the nature of their work, being famously dusty.
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ignis fatuus (n.)
"will o' the wisp, jack-o-lantern," 1560s, Medieval Latin, literally "foolish fire;" see igneous + fatuous. "It seems to have been formerly a common phenomenon; but is now exceedingly rare" [OED].
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apo koinu 

Greek, literally "in common." Applied to sentences with one subject and two predicates; a formation rare in modern English, though it occurs more often in Old English. For the elements, see apo- + koine.

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big time (n.)
"upper reaches of a profession or pursuit," by 1909 in vaudeville slang. As an adjective by 1915. The same phrase was common in colloquial use late 19c.-early 20c. in a broad range of senses: "party, shindig, fun, frolic."
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