Where does “ikkunanpesu” come from?

ikkunanpesu (Finnish) comes from Finnish ikkuna, from Finnish akkuna, from Proto-Finnic *akkuna, from Old East Slavic окъно, from Proto-Slavic okъnò — window.

ikkunanpesu (Finnish): window cleaning

Definitions

window cleaning

Ancestry of “ikkunanpesu”, step by step

ikkunanpesu traces back through two separate lines of ancestry.

via Finnish ikkuna

Step	Language	Word	Meaning
1	Finnish	ikkuna	window; sash
2	Finnish	akkuna	Alternative form of ikkuna
3	Proto-Finnic	*akkuna	window
4	Old East Slavic	окъно	window
5	Proto-Slavic	okъnò	window

via Finnish pesu

Step	Language	Word	Meaning
1	Finnish	pesu	wash, washing
2	Finnish	-u	Forms nouns from verbs. Most common with "e"- and...
3	Proto-Finnic	-u	Forms nouns from adjectives, nouns

Every word from Proto-Slavic okъnò →Every word from Old East Slavic окъно →Every word from Proto-Finnic *akkuna →