Your request has been hanging around for more than a fortnight yet. Sure your idiom is not an everyday one. Crest and bill are both polysemous. I suppose you ran some searches on line without succeeding. Sorry, Iâ€™ve not been more successful than you. It can surely have a wide variety of meanings. If I come across it one day, Iâ€™ll let you know. But maybe the context in which you found it out could help you devising a meaning.
I can't find any reference to this expression anywhere either, sorry! Good luck in your hunt.