parting shot

 

English Wikipedia has an article on:

Parthian shot

Wikipedia

Believed to be a variation of Parthian shot, referring to a military maneuver in which Parthian troops retreating on horseback turned back to face the enemy and shot while retreating.^[1][2]

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parting shot (plural parting shots)

1. (idiomatic) An insult or barbed comment issued as the speaker departs or the conversation comes to an end.
   • 2007 September 18, Greg Stolz, “Power's parting shot at enemies”, in Courier-Mail, Australia:

     Gold Coast Deputy Mayor David Power took a parting shot at the Crime and Misconduct Commission and his council enemies as he announced his bombshell resignation today.

   • 22 March 2012, Scott Tobias, AV Club Cabin Boy[1]

     When news arrives that the school must graduate Nathanial to official “Fancy Lad” status early and put him on the Queen Catherine first class to run the Mayweather in Hawaii, the headmaster dutifully complies, but Nathanial gets in a few parting shots on his way out the door.