Perhaps you should try some spelling variations:
passiver » passiven, passively, passiert
passiverer » passivener, passivelyer, passierter, passiverwerb, passieren, passagerer
passivieren » passivierende, passivierung, passieren
passivener » passiven, passiverwerb

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 (passivieren OR (passiverer OR passivener))) OR passive).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((passiver or (passivieren or (passiverer OR passivener))) or passive)".
• Adding a wildcard symbol may retrieve word variants: ((passiver or (passivieren or (passiverer OR passivener))) or passive)*.