Where does “opin” come from?

opin (Old Frisian) comes from Proto-Germanic upanaz, from Proto-Indo-European upó, from Proto-Indo-European h₃ewp-.

Ancestry of “opin”, step by step

StepLanguageWordMeaning
1Proto-Germanicupanazopen
2Proto-Indo-Europeanupóunder, below
3Proto-Indo-Europeanh₃ewp-—
Every word from Proto-Indo-European h₃ewp- →Every word from Proto-Indo-European upó →Every word from Proto-Germanic upanaz →