/jak"euh nayps'/ , n.
1. an impertinent, presumptuous person, esp. a young man; whippersnapper.
2. an impudent, mischievous child.
3. Archaic. an ape or monkey.
[ 1400-50; late ME Jakken-apes, lit., jack (i.e., man) of the ape, nickname of William de la Pole (1396-1450), Duke of Suffolk, whose badge was an ape's clog and chain ]