Where does “selkäosa” come from?

selkäosa (Ingrian) comes from Ingrian selkä, from Proto-Finnic selkä, from Proto-Finno-Permic śelkä.

Ancestry of “selkäosa”, step by step

StepLanguageWordMeaning
1Ingrianselkäback
2Proto-Finnicselkäback; ridge
3Proto-Finno-Permicśelkä—
Every word from Proto-Finno-Permic śelkä →Every word from Proto-Finnic selkä →Every word from Ingrian selkä →