Where does “keskinäisesti” come from?

keskinäisesti (Finnish) comes from Finnish keskinäinen, from Finnish Keski-, from Proto-Finnic keski, from Proto-Finno-Permic keske.

keskinäisesti (Finnish): mutually

Definitions

Step	Language	Word	Meaning
1	Finnish	keskinäinen	mutual
2	Finnish	Keski-	—
3	Proto-Finnic	keski	middle, center
4	Proto-Finno-Permic	keske	—

keskinäisesti — Etymology, Origin & Word History | Etymology Explorer