Renaming Bluetooth device not working
Of course there is a .plist file to (backup and) delete.


First of all close your Mac's Bluetooth
Open Finder
From toolbar select -> Go -> Go To Folder
Copy paste this path /Library/Preferences
Locate the file com.apple.Bluetooth.plist and rename it to
com.apple.BluetoothOLD.plist
Then do the step 3 again and
Copy paste this address ~/Library/Preferences/ByHost
Locate a file that starts with com.apple.Bluetooth... and rename
it.
Restart your Mac
Re-enable your Bluetooth and try again