They are both multinational publicly traded corporations that originated in Germany. If you have to describe their “nationality” (a problem with multinational corporations), you could say they are European (referring to the EU, not the continent).
If you want to boycott companies based on World War II, you probably should make all your own products from scratch, and avoid all retailers (remember, we now know that the Allies knew about the holocaust from the “get go” and avoided trying to interfere).