Yes, it's quite the mystery! "Baby carriage" maybe ... but "baby cart" ... never!

I'd always assumed it was a literal translation from an uninformed non-native English speaker. For this explanation to be plausible though, we need to find a language (or country) in which "baby cart" is the idiomatic way to say "pram" - anyone know one?

Searching urban dictionary suggests it might have been chosen for its lewd connotations - which is consistent with the infamous goatse secret operator. I think it's time to ask the BooK.