cnafa

Old English cnafa meant a boy, a young man, or a male child — a perfectly respectable term for a youth. The word has cognates in Old High German (knabo) and Old Norse (knapi, a page or squire), all meaning a young male person. Knave was the ordinary word for a boy before boy arrived in the language around 1300.

As boy displaced knave for the simple meaning of male child, knave drifted toward its secondary meaning — male servant — and then, by semantic derogation, toward rogue and scoundrel. The process is well-documented: words for servants and lower-status males often drift toward negative connotations in English and other languages. By the 14th century, Chaucer was using knave for a rogue, a trick, a villainous person.

The knave in a deck of playing cards — now usually called the Jack — preserves the servant meaning. The knave was the servant figure in medieval card decks, ranking below the queen and king. In English card games, knave was the standard term until jack (originally a nickname for a low-status male) began replacing it in the 18th century. Many British card players still say knave.

The progression from boy → servant → rogue follows a social prejudice embedded in English: the word for a lower-status male becomes the word for an untrustworthy one. The same shift happened to churl (peasant → rude person), villain (farmhand → criminal), and several others. Low social status was moralized into bad character.