Perhaps you should try some spelling variations:
passiver » passive, passively, passiert
passiverer » passiveer, passivelyer, passierter, passiverwerb, passivieren, passieren
passiveeren » passivieren, passieren, passivierende
passiven » passive, passion

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: ((passiver OR (passiveeren OR passiverer)) OR passiven).
• Adding a wildcard symbol may retrieve word variants: ((passiver or (passiveeren or passiverer)) or passiven)*.