When I mount the Truecrypt file on my USB drive it shows up as truecrypt1.

The volume is FAT, using mtools to rename a volume label involves e2label /dev/sdbx, however truecrypt1 does not map to a physical partition. fdisk -l does not show the volume partition (only the physical USB device), and df -h lists the volume path as /dev/mapper/truecrypt1.

Finally, using the Nautilus 'Rename' context action, gives the error: "Sorry, could not rename "truecrypt1" to "towel": Operation not supported by backend".

Apparently this can be done in Win, but how can I rename this volume in Ubuntu?

As Nicolas said, specifying the mount point names the partition the same. The truecrypt GUI does not remember the mount point I set, so I specify the mount points in a script which I placed in my main menu.

#!/bin/bash
gksudo truecrypt /media/usbdrive/encryptedfile /media/securedata/