"male ass," 1727, from jack (n.) + ass (n.1). Contemptuous meaning "stupid person" is attested from 1823. Related: Jackassism (1837, American English); jackassery (1833).
jack
Jack Russell
jackal
jackanapes
jackaroo
jackass
jackboot
jackdaw
jacket
jack-hammer
jack-in-the-box
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