From Wiktionary, the free dictionary
From fallen (“to fall”) + Tür (“door”).
Falltür f (genitive Falltür, plural Falltüren)
- trapdoor
Declension of Falltür [feminine]
- “Falltür” in Duden online
- “Falltür”, in Digitales Wörterbuch der deutschen Sprache[1] (in German)