Where does “sotilaslähetti” come from?

sotilaslähetti (Finnish) comes from Finnish sotilas, from Finnish -las, from Finnish -lä, from Finnish -as, from Proto-Finnic -s, from Proto-Finno-Ugric -s.

Ancestry of “sotilaslähetti”, step by step

sotilaslähetti traces back through two separate lines of ancestry.

via Finnish sotilas

Step	Language	Word	Meaning
1	Finnish	sotilas	soldier; pawn; jack, knave
2	Finnish	-las	Forms nouns used to describe people; Forms...
3	Finnish	-lä	Front vowel variant of -la
4	Finnish	-as	Forms some adjectives; Forms some nouns
5	Proto-Finnic	-s	Forms nouns
6	Proto-Finno-Ugric	-s	—

via Finnish lähetti

Step	Language	Word	Meaning
1	Finnish	lähetti	messenger, courier; orderly; errand boy
2	Finnish	lähettää	to send; to dispatch; to ship
3	Finnish	-ttaa	Forms causative verbs. May be applied to verbs...
4	Proto-Finnic	-ttadak	Creates causative verbs from regular verbs,...
5	Proto-Uralic	-kta-	—

Every word from Proto-Finno-Ugric -s →Every word from Finnish -lä →Every word from Finnish -las →