This seems to have answered a longstanding question I had about French surnames. I had come across a presentation given by a person bearing the name "La Rochefoucauld" and I always wondered if she was descended from the eponymous noble family or related to the famous writer. This website tells me that in France the name "La Rochefoucauld" is uncommon but not rare so I guess the answer to that question is "maybe".

I also searched for "Monteverdi" out of curiosity and the largest cluster bearing that name are in Lombardy centred around Cremona, which was indeed where the famous composer was born four and a half centuries ago.