There are many better names than
Josiah if you want a son called
Joe.
Joseph itself, and
Joel (which I'd use if
Joseph wasn't a family name).
Josiah is just plain old.
Luna is too close to 'loony' and once again there are alternatives:
Selena and
Diana are both preferable.
Btw, I've met a
Luna who must be close to retirement age by now. Pleasant enough person, bright in her way (an academic) and perhaps too feisty. She didn't inspire any major love or hatred for the name, but I wouldn't consider it for one moment anyway.