A stand-in that fills the bill.
Dear Word Detective: In many a novel I’ve read of people delivering a “parting shot” in the form of “a threat, insult, condemnation, sarcastic retort, or the like, uttered upon leaving.” Imagine my surprise when I recently started reading the Sherlock Holmes novels for the first time (rather than watching a movie) and found the famous detective firing a “Parthian shot” instead! (“With which Parthian shot he walked away, leaving the two rivals open-mouthed behind him.” — A Study in Scarlet) I immediately consulted with my trusty 1960s Watson — er, Webster — where I found the second phrase explained. Apparently, the ancient Parthian archers were famous for a particular horseback maneuver in which they feigned a retreat, then fired backward at the pursuing enemy. As a longtime reader of your columns, I smelled folk etymology right away. Obviously, “parting shot” had to be a corruption of “Parthian shot,” right? But when I later looked up the matter on the Internet, I became doubtful. It seems that the chronological order of the appearance of the two phrases is not quite clear. But since my sources are by no means reliable (Wikipedia, for one), I turn to you for enlightenment. Surely you, the original Word Detective, could outwit even the great Holmes any time when it comes to word origins. So for your capacity, this small puzzle can be nothing more than elementary. Right? — Holger Maertens, Germany.
Gosh, I love it when people write my column for me. I don’t suppose I could get away with simply saying “Yes” at this point, could I? By the way, Sherlock Holmes in print beats the best movie (or TV) versions by a mile.
With the game well afoot through your detailed exposition, I need only note that the Parthians were the residents of Parthia, an ancient kingdom in what is now Iran, and Parthian horsemen really were famed for their “Parthian shot” fired while turning to retreat. “Parthian shot” has been used in a figurative sense to mean “a final insult or point of argument made as one is leaving” since the mid-19th century.
“Parting shot,” meaning the same thing and based on the sense of “parting” as a noun meaning “the action of leaving,” also dates to the mid-19th century. The underlying sense of “a last remark on your way out the door” is older, however, as “parting blow” is found as early as the 16th century (“Thus much I must say for a parting blow,” 1592).
What we have here, I suspect, is a very convenient coincidence. Given the spotty record of 19th century printed sources, it’s impossible to say with absolute certainty which phrase appeared first, although most authorities assume that “Parthian shot” was the original form. But even in the 19th century, people who knew who the Parthians were and thus truly understood the reference must have been fairly rare, and as the history of the Middle East became more obscure even among educated English speakers in the West, “parting” stepped up to fill the vacancy. This was, as you guessed, a classic case of folk etymology, where a more familiar word is substituted for a word in a phrase which is no longer (or never was) understood by its speakers. Our word “bridegroom,” for instance, was originally “brydguma,” meaning literally “bride-man.” But as the Old English “guma” (man) faded from the popular vocabulary, the more recent and thus familiar “groom” (meaning “male servant”) was substituted. The fact that “parting shot” fit so well with both the sound and the “while leaving” sense of “Parthian shot” made the process unusually seamless.