Basically what it says in the title
I remember reading years ago in some chapter of what I think is a Kurt Vonnegut book, that the Germans have a word for someone you meet who represents who you could become, but would prefer not to, and how that person is significant as a symbol and drives you to become who you should be or want to be.
Did I dream this? What book was it and what was the word?
Gemma is wrong. Or at least I have never heard it as one combined word. As the examples themselves show, it is normally used as adjective+noun. And while you can combine it, I have never seen that till now.
And to OPs question: I don’t know any such word in the German language. It might be a regional thing or it might just be something Vonnegut invented himself.