When you first shoot a clip (or series of short clips) with Cinamatic, the app will give it a generic name.
But that name can be changed.
Start by opening Cinamatic and tapping on the film reel icon to the left of the red record button, on the main screen.
That'll take you to the Unfinished Clips screen.
Then tap on the gear icon to the right of the Clip that you want to rename.
The app will prompt you with a couple of options. Tap the option labelled "Edit Clip Name". The in-app keyboard will pop up and you can edit your clip name. When you’re done just hit Go and then Done.