Where does “*durz” come from?

*durz (Proto-Germanic) comes from Proto-Indo-European dʰwṓr, from Proto-Indo-European dʰwer- — door.

Ancestry of “*durz”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	dʰwṓr	door
2	Proto-Indo-European	dʰwer-	door