Where does “pluris” come from?

pluris (Latin) comes from Latin plūs, from Old Latin plous, from Proto-Indo-European ploh₁is-.

Ancestry of “pluris”, step by step

Step	Language	Word	Meaning
1	Latin	plūs	more; more of
2	Old Latin	plous	—
3	Proto-Indo-European	ploh₁is-	—