Where does “rostfraj” come from?

rostfraj (Serbo-Croatian) comes from German rostfrei, from German frei, from Middle High German vrî, from Old High German frī, from Proto-West Germanic frī, from Proto-Germanic frijaz, from Proto-Indo-European priHós, from Proto-Indo-European preyH- — to love, to please.

rostfraj (Serbo-Croatian): stainless steel