Where does “Ilmari” come from?

Ilmari (Finnish) comes from Finnish Ilma, from Finnish -ri, from Finnish -ra, from Finnish -i, from Proto-Uralic -j — oblique plural.

Ancestry of “Ilmari”, step by step

Step	Language	Word	Meaning
1	Finnish	Ilma	air
2	Finnish	-ri	Used to create names of occupations from nouns or...
3	Finnish	-ra	Forms nouns or adjectives, mostly from nominal...
4	Finnish	-i	A nominal suffix used in eg. ukko → ukki; Used...
5	Proto-Uralic	-j	oblique plural