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earnest [earnest 词源字典]: earnest: [OE] Earnest was originally a much more red-blooded word than it is today. It comes ultimately from a Germanic base *ern- which denoted ‘vigour’ or ‘briskness’. To this was added the noun suffix – ost (earnest was originally a noun), giving Old English eornost, which appears at first to have meant ‘intense passion’, and particularly ‘zeal in battle’. However, by the end of the Old English period there is already evidence of a semantic toning down from ‘intensity of feeling’ to ‘seriousness of feeling’ (as opposed to ‘frivolity’), a process which has culminated in modern English connotations of ‘over-seriousness’.
[earnest etymology, earnest origin, 英语词源]
activity (n.): c. 1400, "active or secular life," from Old French activité, from Medieval Latin activitatem (nominative activitas), a word in Scholastic philosophy, from Latin activus (see active). Meaning "state of being active, briskness, liveliness" recorded from 1520s; that of "capacity for acting on matter" is from 1540s.
brisk (adj.): 1550s, as Scottish bruisk, probably an alteration of French brusque (see brusque). Related: Briskly; briskness.