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.
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).
"one who leads a military patrol in formation in a jungle, etc.," 1944, said to be from point (n.) in military sense of "small leading party of an advance guard" (1580s) + man (n.). A more literal sense also is possible. Point (n.) in U.S. also meant "position at the front of a herd of cattle," and pointman in this sense is attested by 1903.
"small bag used by sailors for needles, thread, scissors, thimble, etc.," 1828, nautical slang, of uncertain origin, perhaps from the alleged British naval phrase commodity bag. Hence also ditty-box (1841).
Every true man-of-war's man knows how to cut out clothing with as much ease, and producing as correct a fit, as the best tailor. This is a necessity on board ship, for the ready-made clothing procured of the purser is never known to fit, being generally manufactured several sizes larger than necessary, in order that it may be re-cut and made in good style. [Charles Nordhoff, "The Young Man-of-War's Man," 1866]
in writing, to indicate the common casual pronunciation of could have, by 1909.
15c. Inca citadel high in the Andes Mountains of Peru, from Quechua (Inca) machu "old man" + pikchu "peak."