Latin word -or comes from Proto-Indo-European *-os

Detailed word origin of -or

Dictionary entry	Language	Definition
*-os	Proto-Indo-European (ine-pro)	Creates nouns from verb stems denoting the performance or action of that verb. Creates action nouns or result nouns from verbs.
* -oss	Proto-Indo-European (ine-pro)
-or	Latin (lat)	Used to form a third-declension masculine abstract noun from a verb root or conceived root form.

Words with the same origin as -or