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concern [concern 词源字典]: concern: [15] In earliest use, English concern meant ‘distinguish, discern’. This was a reflection of its ultimate source, Latin cernere ‘sift, separate’. In combination with the prefix com- ‘together’ it produced concernere, which in classical times meant specifically ‘mix together preparatory to sifting’. Later, however, the prefix seems to have taken on a more intensive role, with concernere reverting to the same range of senses as cernere.

By the Middle Ages these not only included ‘discern, perceive’ and ‘decide’ (whence English certain, from the past participle of cernere), but had widened considerably to ‘relate to’ – a meaning which emerged in English concern in the 16th century. Connotations of distress or worry began to develop in the late 17th century.
=> certain, discern[concern etymology, concern origin, 英语词源]
concert: concert: [16] Concert probably comes ultimately from Latin concertāre, a compound verb formed from the prefix com- ‘with’ and certāre ‘strive, contend’, a verb derived from certus ‘sure, fixed’ (source of English certain), which in turn came from cernere (source of English concern). Some etymologists have rejected concertāre as the origin of concert, on the grounds that its meaning – ‘dispute, debate’ – was completely opposite, but it seems that in post-classical times the Latin verb came to mean ‘strive together (in cooperation)’ – a much more plausible sense relationship.

It passed into Italian as concertare ‘bring into agreement’, and developed specific musical connotations of ‘harmony’. English acquired it via French concerter. The noun concerto [18] was an Italian derivative of the verb; French borrowed it as concert, and passed it on to English as the noun concert [17]. Concertina was coined in the 1830s, from the noun concert.
=> certain, concern, concertina, concerto, disconcert
concern (v.): early 15c., "perceive, distinguish," also "refer to, relate to," from Middle French concerner, from Medieval Latin concernere "concern, touch, belong to," figurative use of Late Latin concernere "to sift, mix, as in a sieve," from Latin com- "with" (see com-) + cernere "to sift," hence "perceive, comprehend" (see crisis). Apparently the sense of the prefix shifted to intensive in Medieval Latin. Meaning "worry" is 17c. Related: Concerned; concerning. Letter opening to whom it may concern attested by 1740.
concern (n.): 1580s, from concern (v.).
concert (n.): 1660s, "agreement, accord, harmony," from French concert (16c.), from Italian concerto "concert, harmony," from concertare "bring into agreement," in Latin "to contend, contest, dispute," from com- "with" (see com-) + certare "to contend, strive," frequentative of certus, variant past participle of cernere "separate, decide" (see crisis).

Before the word entered English, meaning shifted from "to strive against" to "to strive alongside." Sense of "public musical performance" is 1680s. But Klein considers this too much of a stretch and suggests Latin concentare "to sing together" (from con- + cantare "to sing") as the source of the Italian word in the musical sense.
concertina (n.): 1835, from concert + fem. ending -ina. Portable musical instrument invented 1829 by Sir Charles Wheatstone. Concertina wire attested by 1917, so called from similarity to the musical instrument.
concerto (n.): 1730, from Italian concerto (see concert). Concerto grosso is from 1724.
disconcert (v.): 1680s, from Middle French disconcerter (Modern French déconcerter) "confused," from dis- "do the opposite of" (see dis-) + concerter (see concert). Related: Disconcerted; disconcerting; disconcertingly.
unconcerned (adj.): 1630s, from un- (1) "not" + past participle of concern (v.). Related: Unconcernedly.
concertante: "Denoting a piece of music containing one or more solo parts, typically of less prominence than in a concerto", Italian, 'harmonizing', from concertare 'harmonize'.
concertino: "A simple or short concerto", Late 18th century: Italian, diminutive of concerto (see concerto).