Where does “-eis” come from?

-eis (Old French) comes from Vulgar Latin -iscus, from Latin -ensis, from Latin arvum, from Latin colō, from Latin quelō, from Proto-Italic kʷelō, from Proto-Indo-European kʷéleti, from Proto-Indo-European kʷel- — to turn.

-eis (Old French): used to form nationalities; used to form names of...