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aplomb [aplomb 词源字典]: aplomb: [18] Originally, aplomb meant literally ‘quality of being perpendicular’. It was borrowed from French, where it was a lexicalization of the phrase à plomb ‘according to the plumb line’ (plomb came from Latin plumbum ‘lead’, also the ultimate source of English plumb, plumber, plumbago, and plummet). The notion of ‘uprightness’ gave rise in the 19th century to the metaphorical sense ‘composure’.
=> plumb, plumber, plummet[aplomb etymology, aplomb origin, 英语词源]
plumb: plumb: [13] Plumb comes via Old French *plombe from Latin plumbum ‘lead’, a word of uncertain origin. Of its modern English uses, the verbal ‘sound the depths’ comes from the use of a line weighted with lead (a plumb line) to measure the depth of water and the adverbial ‘exactly’ from the use of a similar line to determine verticality. Related words in English include aplomb; plumber [14] (originally simply a ‘worker in lead’, but eventually, since water pipes were once made of lead, a ‘pipe-layer’); plummet [14] (a diminutive form coined in Old French); and plunge [14] (from the Vulgar Latin derivative *plumbicāre ‘sound with a plumb’).
=> aplomb, plumber, plummet, plunge
aplomb (n.): "assurance, confidence," 1828, from French aplomb (16c.), literally "perpendicularity," from phrase à plomb "poised upright, balanced," literally "on the plumb line," from Latin plumbum "(the metal) lead" (see plumb (n.)), of which the weight at the end of the line was made.
perpendicular (adj.): late 15c., from adverb (late 14c.), from Old French perpendiculer, from Latin perpendicularis "vertical, as a plumb line," from perpendiculum "plumb line," from perpendere "balance carefully," from per- "thoroughly" (see per) + pendere "to weigh, to hang" (see pendant). As a noun from 1570s. Related: Perpendicularly; perpendicularity.