Are yams and sweet potatoes the same?
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]