You all have some interesting names:
So I have a few for you:
1) Cash as in Johnny
2) Nash as in picking on Johnny
3) Flash as in lightening
Just pick something that is cute and suits him. It will come to you in time, but I will say a 4 week old pup is too young to leave mom. He may end up with a few issues from that. So, I would go with Nash or Cash. But that's my thoughts. Good luck with your 4 legged freind