- an impertinent, presumptuous person, especially a young man; whippersnapper.
- an impudent, mischievous child.
- Archaic. an ape or monkey.
- a conceited impertinent person
- a mischievous child
- archaic a monkey
mid-15c., “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. See note in OED.