Where does “läjäpäissä” come from?

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

Ancestry of “läjäpäissä”, step by step

läjäpäissä traces back through two separate lines of ancestry.

via Finnish pää

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

via Finnish läjä

StepLanguageWordMeaning
1Finnishläjäheap, pile collection of things laid in a body, or thrown together so as to form an elevation
2Finnishläjähtääto make a slapping sound of a flat object, to splat, to splash
Every word from Proto-Uralic päŋe →Every word from Proto-Finnic pää →Every word from Finnish pää →