Where does “Pääjärvi” come from?

Pääjärvi (Finnish) comes from Finnish pää, from Proto-Finnic pää, from Proto-Uralic päŋe — head.

Ancestry of “Pääjärvi”, step by step

Pääjärvi traces back through two separate lines of ancestry.

via Finnish pää

StepLanguageWordMeaning
1Finnishpäähead; end, tip
2Proto-Finnicpäähead
3Proto-Uralicpäŋehead

via Finnish järvi

StepLanguageWordMeaning
1Finnishjärvilake
2Latin-lanominative feminine singular of -lus; nominative...
Every word from Proto-Uralic päŋe →Every word from Proto-Finnic pää →Every word from Finnish pää →