Where does “ro” come from?

ro (Old French) comes from Latin raucus, from Latin -cus, from Proto-Italic -kos, from Proto-Indo-European -ḱos — -y, -ic.

Ancestry of “ro”, step by step

StepLanguageWordMeaning
1Latinraucushoarse; harsh, rough, grating, husky; raucous
2Latin-cussuffixed to nouns, forms adjectives; This suffix...
3Proto-Italic-kos—
4Proto-Indo-European-ḱos-y, -ic

Words derived from “ro”

Every word from Proto-Indo-European -ḱos →Every word from Latin -cus →Every word from Latin raucus →