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1859, thieves' slang, "counterfeit, sham, bad, spurious," of unknown origin. Of persons, "cunning, sharp," from 1883. Sense of "sneering" is first attested 1933, perhaps via sense of "hypocrisy, malicious gossip" (1902). Related: Sneeringly.
Contemptible; mean; nasty, esp in an insinuating way • Now used nearly exclusively in reference to remarks and persons who make them: A woman gets nothing but snide remarks about her driving skills
[1859+; origin unknown]