Where does “Руан” come from?

Руан (Russian) comes from French Rouen, from Old French Roem, from Latin Rotomagus, from Gaulish Ratumacos, from Gaulish magos, from Proto-Celtic magos, from Proto-Indo-European meǵh₂- — big, great; great; big, stour, great.

Ancestry of “Руан”, step by step

StepLanguageWordMeaning
1FrenchRouen—
2Old FrenchRoem—
3LatinRotomagusThe chief city of the Veliocasses in Gallia Lugdunensis, now Rouen
4GaulishRatumacos—
5Gaulishmagosfield
6Proto-Celticmagosplain, field
7Proto-Indo-Europeanmeǵh₂-big, great; great; big, stour, great
Every word from Proto-Indo-European meǵh₂- →Every word from Proto-Celtic magos →Every word from Gaulish magos →