Where does “eroaminen” come from?

eroaminen (Finnish) comes from Finnish erota, from Finnish ero, from Finnish -o, from Proto-Finnic -o, from Proto-Uralic -w.

Ancestry of “eroaminen”, step by step

Step	Language	Word	Meaning
1	Finnish	erota	to divorce; to differ, be different; to resign
2	Finnish	ero	difference, distinction; Short for avioero;...
3	Finnish	-o	Forms result or action nouns from verbs; Forms...
4	Proto-Finnic	-o	Forms action/result nouns from verbs
5	Proto-Uralic	-w	—