Sometimes renaming internal or external hard disk you risk to make the disk unusable and lose data.
For the specific case is better to copy\paste in safe place all the data from your usb drive.
Then right click on the usb drive,click format,choose quick format,in the Volume Label space write the name you like,click start to format the drive with the new name.
As you can see in my attachments my usb drive name was MULTIBOOT and i format\rename it to PANAIS.
with this and post back