late 14c., nowghty, noughti "needy, having nothing," also "evil, immoral, corrupt, unclean," from nought, naught "evil, an evil act; nothingness; a trifle; insignificant person; the number zero" (from Old English nawiht "nothing;" see naught)) + -y (2).
Specific meaning "sexually promiscuous" is from 1869. The mitigated sense of "disobedient, bad in conduct or speech, improper, mischievous" (especially of the delinquencies of children) is attested from 1630s. Related: Naughtily; naughtiness. In 16c.-18c. a woman of bad character might be called a naughty pack (also sometimes used of men and later of children).