I'm not disputing it's a plural
I suspect that someone noticed the word vagina and being a smug git, proclaimed that the plural be vaginae rather than vaginas "so it fits the rule".

The same sort of smug gits who say prospecti instead of prospectuses.
( sandettie light vessel automatic New Twitter - @bollocksreally, Mon 6 Dec 2010, 12:49, 1 reply, 15 years ago)

Though
the plural of verruca is verrucae, which kind of ruins the advert's tagline "bazooka those verrucas". Accurately, it should be 'Bouzouki those verrucae"
( sandettie light vessel automatic New Twitter - @bollocksreally, Mon 6 Dec 2010, 12:52, Reply)

OK
Vagina is a medical word coined the 1680's. It comes from the Latin vagina meaning a scabbard or sheath. So I think we can assume the plural has always been vaginae, as I can't imagine a 17th century man of medicine anglicising the plural when at that time nearly all scientific and medical writings were written in classical Greek or Latin, English being considered a peasants language.
( The Awful Puppy Bakery is still bored, Mon 6 Dec 2010, 13:07, Reply)

Now you mention it
scabbard is a far better word.
( sandettie light vessel automatic New Twitter - @bollocksreally, Mon 6 Dec 2010, 18:38, Reply)

Wasn't it "Bazooka that verruca" ?

(MrOli is ugly, but in the morning you will be sober, Tue 7 Dec 2010, 12:40, Reply)

What if you only have one bazookum?

(Vice Admiral Sir Charles Cockbrush KCB MBE DSO, who is finding it increasingly difficult to log into b3ta.com wants to duck your aunt and kick your puppy, Tue 7 Dec 2010, 16:17, Reply)