French word kirsch comes from German Wasser

Detailed word origin of kirsch

Dictionary entry	Language	Definition
Wasser	German (deu)	An alcoholic beverage, similar to brandy, made from fermented fruit. Water.
Kirschwasser	German (deu)	A distilled spirit made from cherries, usually of the variety Cerasus avium; kirsch.
kirsch	French (fra)	Kirsch.