Where does “lisäjoki” come from?

lisäjoki (Finnish) comes from Finnish lisä-, from Finnish lisä, from Proto-Finnic lisä, from Proto-Finno-Permic lisä.

Ancestry of “lisäjoki”, step by step

StepLanguageWordMeaning
1Finnishlisä-extra, auxiliary, supplemental, additional
2Finnishlisäaddition, increase, supplement
3Proto-Finniclisäaddition, increase
4Proto-Finno-Permiclisä—
Every word from Proto-Finno-Permic lisä →Every word from Proto-Finnic lisä →Every word from Finnish lisä →