Premiere: Renaming cameras in a multi-camera sequence
When you create a Multi-Cam sequence, the prompt will give you the option to name the cameras based on the track or clip name.



I don't believe there is a way to rename the cameras after setting up Multi-Cam.

One other option would be to put each clip into a sequence with a text layer as an overlay. After you have finished arranging your Multi-Cam composition, the text layer can be hidden or deleted.