Well, here is a hint from Jonathan:
Hint #1 One of the names begins with either an A or a B!!
I should add that at this time, we are neither confirming nor denying any guesses.
We decided for sure the night we registered at Babies R us. We had been trying it out for a few days, and Jonathan was calling her "_________". I finally said that we either had to make it official or he had to stop calling her that name. So, we made it official. We thought it would be fun to keep the name a secret for a little bit. We aren't holding out on everyone until she gets here, so don't worry. It'll only be a little while.