e2label - Change the label on an ext2/ext3/ext4 filesystem
If you forgot to give a LABEL to a partition, this tool can do it. LABELs are great, you can mount a labeled partition with e.g.
sudo mount LABEL=somename /mnt # ignoring other options in this example
and not have to use things like /dev/sdb3 or UUID=“a-very-long-string”.