MinecraftNameChecker
I used this to check the availability of OG Names for Labymod but this can also used to fetch names in General, you can find the Labymod OG list here: https://github.com/LabyMod/og-names
Usage: Create a File named Names.txt and write the names you want to check in (new line = new name). After all checks are done it writes all Names to a new txt called Available.txt