Where does “*ōʀ” come from?

*ōʀ (Proto-West Germanic) comes from Proto-Germanic ōsaz, from Proto-Indo-European h₃éh₁os — mouth.

Ancestry of “*ōʀ”, step by step

Step	Language	Word	Meaning
1	Proto-Germanic	ōsaz	mouth; mouth, inlet
2	Proto-Indo-European	h₃éh₁os	mouth