Where does “Oest-Loega” come from?

Oest-Loega (Dutch) comes from Russian Усть-Луга, from Russian у́стье, from Proto-Slavic ustьje, from Proto-Slavic ustà, from Proto-Indo-European h₃éh₁os — mouth.

Ancestry of “Oest-Loega”, step by step

StepLanguageWordMeaning
1RussianУсть-Лугаthe town is placed on mouth of river Luga, where this river falls into the Gulf of Finland
2Russianу́стьеmouth, outflow, discharge, issue
3Proto-Slavicustьjemouth, rivermouth
4Proto-Slavicustàlips, mouth
5Proto-Indo-Europeanh₃éh₁osmouth
Every word from Proto-Indo-European h₃éh₁os →Every word from Proto-Slavic ustà →Every word from Proto-Slavic ustьje →