Originally in German (about 1820), it appears that it came into English use at the beginning of the 20th Century (it’s fun to say that).

It’s the official name for the “coming of age” genre.

How did this word get in my head? Search “every experience in life has value” with quotes, and all you get is new age-y and christian sites. The phrase popped into my head and made me think of Maugham or Lawrence novels; THEN I decided I needed to know the genre, hence the Bildungsroman.