an impertinent, presumptuous person, esp. a young man; whippersnapper.
2.
an impudent, mischievous child.
3.
Archaic. an ape or monkey.
Origin: 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
c.1449, "a monkey," also "an impertinent, conceited fellow;" apparently from Jack of Naples, but whether this is some specific personification or folk etymology of jack (n.) + ape is unknown.