Where does “guo-” come from?

guo- (Old Welsh) comes from Proto-Brythonic gwo-, from Proto-Celtic uɸo-, from Proto-Indo-European upó, from Proto-Indo-European h₃ewp-.

Ancestry of “guo-”, step by step

StepLanguageWordMeaning
1Proto-Brythonicgwo-sub-, under
2Proto-Celticuɸo-sub-, under
3Proto-Indo-Europeanupóunder, below
4Proto-Indo-Europeanh₃ewp-—

Words derived from “guo-”

Every word from Proto-Indo-European h₃ewp- →Every word from Proto-Indo-European upó →Every word from Proto-Celtic uɸo- →