it doesn't just have to be grape wine either

People in my country make hard spirits out of various fruits, but mostly plums, and in English those are being translated as fruit brandy.

Although if you want to make cognac (a type of brandy), it has to be grape wine.

Cognac, like Champagne, is about where it's made, not just the recipe. I has to be made out of specific varieties of grapes harvested and fermented in the Cognac area in France. You can import the same grapes and follow the same recipe, but you're not allowed to name it Cognac if you made it outside that area.