It looks like a Berkeley database file (because that's what it is), and renaming it won't fool anyone (which is to be expected, since renaming files never fools anyone). You should be using encryption to hide things you want hidden, not some stupid trick like this. Note that Bitcoin's built-in wallet encryption only encrypts the wallet's private keys (preventing anyone from spending your coins without the passphrase), it does not hide the fact that it is a wallet or even your public addresses. Encrypt your wallet again with another program (such as TrueCrypt) if you want to hide it.