Extraponym
An extrapolated name for something that is yet to have a proper name, or will have its name changed after the fact.
Person 1: World War 3 is gonna be crazy!
Person 2: We don’t even know what it will be called yet, you should stop using extraponyms. Anyways, I’m pretty sure it will be The Great Robot War.
Person 2: We don’t even know what it will be called yet, you should stop using extraponyms. Anyways, I’m pretty sure it will be The Great Robot War.