(n.) a final comment, a cutting remark said on leaving
A lovely little etymological tale popped up on HH today: a parting shot was originally a Parthian shot—a reference to the skilled horsemen and archers of the ancient Parthian Empire.
Parthia was an ancient region of western Asia, roughly equivalent to what is now Iran. The Parthian people were known as fierce warriors and horsemen, and that exceptional military ability helped them to both hold back the encroaching Roman Empire until the 2nd century AD, and to establish a powerful empire of their own, that at its greatest extent stretched from the Caspian Sea in the north to what is now Turkey and the Caucasus mountains in the west; to the Gulf States in the south; and to modern-day Pakistan and Afghanistan in the east.
As both expert archers and horsemen, the Parthians cultivated a talent for aiming and firing arrows while essentially riding blind, turning backwards in their saddles to continue firing at their enemies while ostensibly retreating from battle. It was a clever tactic that not only won them countless battles, but earned them a place in history—and in the collective consciousness of later writers and historians.
Long after their empire collapsed, tales of the Parthian’s extraordinary feigned retreats led writers in the 1600s to use the word Parthian to refer to anything done while leaving, while concluding, or at the very last moment. Tales of their backwards-facing archery likewise led to the term Parthian shot being coined in the early 1800s to refer, originally, to an actual shot fired at the last moment, and later, more figuratively, to a cutting remark or comment delivered immediately prior to or at a moment of departure.