My family go back to the 1300's in a tiny village of Eiken in canton Aargau. The name is very popular, because in German spaeking areas it means "mountain dweller" and in French areas "shepherd", both of which are popular jobs and old family names. Though some are related, many actually are not. The branches are even wider now, and actually began between France and Russia - sorry to dissapoint you.
I have the Familiennamenbuch die Schweiz which lists details for Swiss families with living descendants as at 1960. There are many entries for Berger, and variations.
If I can be of any help let me know. My family were only in Eiken, then our branch came to Australia in the 1860's. There are living relatives in Switzerland, and I do have 2 books on Eiken as well.