Where does “geçiş” come from?

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

Ancestry of “geçiş”, step by step

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

geçiş — Etymology, Origin & Word History | Etymology Explorer