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calm [calm 词源字典]: calm: [14] The underlying meaning of calm seems to be not far removed from ‘siesta’. It comes ultimately from Greek kauma ‘heat’, which was borrowed into late Latin as cauma. This appears to have been applied progressively to the ‘great heat of the midday sun’, to ‘rest taken during this period’, and finally to simply ‘quietness, absence of activity’. Cauma passed into Old Italian as calma, and English seems to have got the word from Italian.
[calm etymology, calm origin, 英语词源]
mousy (adj.): 1812 with reference to quietness; 1853, of color; from mouse + -y (2).
quiet (adj.): late 14c., "peaceable, at rest, restful, tranquil," from Old French quiet and directly from Latin quietus "calm, at rest, free from exertion," from quies (genitive quietis) "rest" (see quiet (n.)). As an adverb from 1570s. Related: Quietly; quietness.
still (n.2): c. 1200, "a calm," from still (adj.). Sense of "quietness, the silent part" is from c. 1600 (in still of the night). Meaning "a photograph" (as distinguished from a motion picture) is attested from 1916.
tranquility (n.): also tranquillity, late 14c., from Old French tranquilite "peace, happiness" (12c.), from Latin tranquillitatem (nominative tranquillitas) "quietness, stillness; serenity," from tranquillus "quiet, calm, still," perhaps from trans- "over" (here in its intensive sense of "exceedingly") + a root possibly related to quies "rest" (see quiet (n.)).
inquietude: "Physical or mental restlessness or disturbance", Late Middle English (in the sense 'disturbance of one's quietness or rest'): from Old French, or from late Latin inquietudo, from Latin inquietus, from in- 'not' + quietus 'quiet'.