knave

a deceitful and unreliable scoundrel

A boy; especially, a boy servant.

Old French: knaveux (naughty)

“We require, I said, a protection that the polite world of Great Britain does not now afford us against the aggressions of the knave, the fool, and the brute.”

— George Meredith, Complete Project Gutenberg Works of George Meredith

“The ranks (from highest to lowest in bridge and poker) are ace, king, queen, jack (or knave), and the numbers from ten down to two (or deuce).”