Green’s Dictionary of Slang

jack n.2

[abbr. SE jackass]

1. [14C–17C; 20C+] a fool.

2. [1900s] (US Und.) a drunk individual who is made the victim of a theft.

In compounds

jack act (v.) [SE jackass]

[1920s+] (Irish) to play the fool; thus jack-acting n.

In phrases

lay on the jack (v.)

[16C] to beat or scold severely.

play the jack (v.)

1. [17C] to act the villain. [play on jack = the ‘knave’ in cards].

2. [19C] to play the fool.