Where does “tarkkaileminen” come from?

tarkkaileminen (Finnish) comes from Finnish tarkkailla, from Finnish tärkätä, from Swedish stärka, from Swedish stärk, from Old Swedish starker, from Old Norse sterkr, from Proto-Germanic starkuz, from Proto-Germanic sterkaną — rigid, stiff; to love.

Ancestry of “tarkkaileminen”, step by step

StepLanguageWordMeaning
1Finnishtarkkaillato watch, to observe, to monitor
2Finnishtärkätäto starch
3Swedishstärkato strengthen; to starch, to apply laundry starch
4Swedishstärkstrong
5Old Swedishstarkerstiff, rigid; steady; strong
6Old Norsesterkrstrong
7Proto-Germanicstarkuzstiff; rigid; strong
8Proto-Germanicsterkanąto become stiff, stiffen
9Proto-Indo-Europeansterg-rigid, stiff; to love
Every word from Proto-Indo-European sterg-Every word from Proto-Germanic sterkanąEvery word from Proto-Germanic starkuz