downbeat (n.)

also down-beat, 1876, "the first note of a measure of music" (as indicated by the downward stroke of a conductor's baton or hand). It is attested by 1952 as an adjective in the figurative sense of "pessimistic," but that is probably via associations of the word down (adv.), because the beat itself is no more pessimistic than the upbeat is optimistic.

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