Where does “işlev” come from?

işlev (Turkish) comes from Turkish iş, from Ottoman Turkish ایش, from Proto-Turkic īĺč — work.

işlev (Turkish): function

Definitions

Step	Language	Word	Meaning
1	Turkish	iş	work, task, deed; job, employment; matter,...
2	Ottoman Turkish	ایش	work
3	Proto-Turkic	īĺč	work

işlev — Etymology, Origin & Word History | Etymology Explorer