The Collaborative International Dictionary of English v.0.48:

Knave \Knave\ (n[=a]v), n. [OE., boy, servant, knave, AS. cnafa
   boy, youth; cf. AS. cnapa boy, youth, D. knaap, G. knabe boy,
   knappe esquire, Icel. knapi, Sw. knape esquire, kn[aum]fvel
   knave.]
   1. A boy; especially, a boy servant. [Obs.] --Wyclif.
      Chaucer.
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            O murderous slumber,
            Lay'st thou thy leaden mace upon my boy
            That plays thee music ? Gentle knave, good night.
                                                  --Shak.
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   2. Any male servant; a menial. [Obs.] --Chaucer.
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            He's but Fortune's knave,
            A minister of her will.               --Shak.
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   3. A tricky, deceitful fellow; a dishonest person; a rogue; a
      villain. "A pair of crafty knaves." --Shak.
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            In defiance of demonstration, knaves will continue
            to proselyte fools.                   --Ames.
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   Note: "How many serving lads must have been unfaithful and
         dishonest before knave -- which meant at first no more
         than boy -- acquired the meaning which it has now !"
         --Trench.
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   4. A playing card marked with the figure of a servant or
      soldier; a jack; as, the knave of hearts.
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   Knave child, a male child. [Obs.] --Chaucer.

   Syn: Villain; cheat; rascal; rogue; scoundrel; miscreant.
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