momentyoudaoicibaDictYouDict[moment 词源字典]
moment: [14] As the closely related momentum [17] suggests, ‘movement’ is the etymological notion underlying moment. It comes via Old French moment from Latin mōmentum. This was a contraction of an assumed earlier *movimentum, a derivative of movēre ‘move’ (source of English move), and it had a wide range of meanings: from the literal ‘movement’ (preserved in English in the directly borrowed momentum) developed the metaphorical ‘instant of time’ (which arose from the notion of a particle so small as only just to ‘move’ the pointer of a scale) and ‘importance’ – both preserved in English moment.

The former has been allotted the derived adjective momentary [16], the latter momentous [17].
=> momentous, momentum, move[moment etymology, moment origin, 英语词源]
moment (n.)youdaoicibaDictYouDict
mid-14c., "very brief portion of time, instant," in moment of time, from Old French moment (12c.) "moment, minute; importance, weight, value" or directly from Latin momentum "movement, motion; moving power; alteration, change;" also "short time, instant" (also source of Spanish, Italian momento), contraction of *movimentum, from movere "to move" (see move (v.)). Some (but not OED) explain the sense evolution of the Latin word by notion of a particle so small it would just "move" the pointer of a scale, which led to the transferred sense of "minute time division." Sense of "importance, 'weight' " is attested in English from 1520s.

Phrase never a dull moment first recorded 1889 in Jerome K. Jerome's "Three Men in a Boat." Phrase moment of truth first recorded 1932 in Hemingway's "Death in the Afternoon," from Spanish el momento de la verdad, the final sword-thrust in a bull-fight.