Where does “Osmo” come from?

Osmo (Galician) comes from Proto-Celtic uxsamo-, from Proto-Celtic owxs-, from Proto-Indo-European h₃ewps-.

Ancestry of “Osmo”, step by step

StepLanguageWordMeaning
1Proto-Celticuxsamo-the uppermost
2Proto-Celticowxs-—
3Proto-Indo-Europeanh₃ewps-—
Every word from Proto-Indo-European h₃ewps- →Every word from Proto-Celtic owxs- →Every word from Proto-Celtic uxsamo- →