knave

Etymology

From Middle English knave, knafe, from Old English cnafa (“child, boy, youth; servant”), from Proto-West Germanic *knabō. Cognate to Dutch knaap and German Knabe.

noun

1. (archaic) A boy; especially, a boy servant.
2. (archaic) Any male servant; a menial.
3. A tricky, deceitful fellow; a dishonest person.
   God's bones! Whenever I go to beat those knaves / my tapsters, out she [my wife] comes with clubs and staves, / "Go on!" she screams — and it's a caterwaul — / "You kill those dogs! Break back and bones and all!" 1951, Geoffrey Chaucer, translated by Nevill Coghill, The Canterbury Tales: Translated into Modern English (Penguin Classics), Penguin Books, published 1977, page 204
4. (card games) A playing card marked with the figure of a servant or soldier; a jack.