Where does “asiain” come from?

asiain (Finnish) comes from Finnish asia, from Proto-Finnic acja — matter, case.

asiain (Finnish): Genitive plural form of asia

Definitions

Step	Language	Word	Meaning
1	Finnish	asia	issue, matter, affair, concern, business,...
2	Proto-Finnic	acja	matter, case

asiain — Etymology, Origin & Word History | Etymology Explorer