It's been a good week for parting shots. On this website, we had Sven Goran Eriksson's decision to take 17-year-old Theo Walcott to the World Cup. Elsewhere, the Times had a Labour councillor offering a parting shot after he was ejected from office in last Thursday's local elections. The second closely matches Collins's definition of "a hostile remark or gesture delivered while departing", but what interested me was that the Collins entry comes under "Parthian shot", not "parting shot".

It's a commonplace of this sort of column that the expression Parthian shot alludes, as Collins puts it, "to the custom of Parthian archers who shot their arrows backwards while retreating". (Didn't the Normans do the same at Hastings? Should we call it a Norman shot?) But in both cases from the last week, the reference was to "parting shots".

There's a certain type of person - the type that writes an etymology column perhaps - who would tell you that this usage is "a bastardization", that these people "meant" Parthian shot, but for some reason lacked the sophistication to foist allusions to first-century Middle Eastern cavalry on their readers. This is the kind of thing that gives people like me a bad name.

Firstly, because Collins doesn't even have an entry for "parting shot", anyone looking up this perfectly common and useful expression would draw a blank unless they had a classical scholar to hand. Secondly, and more importantly, because a quick glance in the OED reveals a first use of "parting shot" in 1835, whereas "Parthian shot" doesn't make it in before 1842, delivering a damaging blow to the idea that "Parthian shot" is the "original" expression, and to the idea that the English language is in inexorable decline.

As far as I'm concerned if you want to say parting shot, I will know exactly what you mean, and will spare you the reference to Gibbon. For reasons to do with being a terrible ponce, however, I reserve the right to use "Parthian shot" myself. Not that this is one, by the way.