Where does “-os” come from?

-os (Old French) comes from Latin -osus, from Old Latin -osos, from Latin ont-to-s, from Latin -o-wont-to-s.

-os (Old French): Alternative form of -us; -ous

Definitions

Step	Language	Word	Meaning
1	Latin	-osus	-ose, -ous; full of, overly, prone to
2	Old Latin	-osos	accusative masculine plural of -ōsus
3	Latin	ont-to-s	—
4	Latin	-o-wont-to-s	—