I'm from Austria and therefore pronounce it the German way in my head and I really dont like the sound of it it's like you said a really old name and old fashionedIt’s actually a very old German name. It originates in old high German which was used 750-1050. Because at time the Ottonen (actually House Ludolfing) ruled as emperors and many of their men were called Otto, it’s a good bet that the female form got traction then. Not in fashion anymore but for some old peerage families (same goes for the male counterpart Otto). I will say, I snicker every time people come up with an English pronunciation. It just doesn’t work. Ottilie has 4 syllables O-tti-li-e and as i and e are almost pronounced the other way round the English way really grates my ears. I have seen it in France but their pronunciation works. The more common French version is Odile though.