Where does “leiskaus” come from?

leiskaus (Finnish) comes from Finnish leiskahtaa, from Finnish leiskua, from Finnish lieska, from Proto-Slavic lěska, from Proto-Slavic *lě̄skà — hazel.

Ancestry of “leiskaus”, step by step

StepLanguageWordMeaning
1Finnishleiskahtaato flame, to flare up, to flush
2Finnishleiskuato flame produce flames; flutter like a flame
3Finnishlieskaflame
4Proto-Slaviclěskahazel
5Proto-Slavic*lě̄skàhazel
Every word from Proto-Slavic *lě̄skà →Every word from Proto-Slavic lěska →Every word from Finnish lieska →