Mmm.... sure? I thought it was Philosophiæ Doctor, as in "some bloke who teaches philosophy"
It may be to some long-dead Latin speaker.
I translated for you. "some bloke who Philosophises about a subject" would be OK.
Point is, Medical Doctorates are a more recent invention than the non-medical (e.g. scientific) version.
Don't forget that Doctorates can also be for many other reasons. I have a friend who has a Doctrate in religion. He studies "the afterlife" (to simplify). He is known by many of us as Doctor Death.