Where does “یاشیل” come from?

یاشیل (Chagatai) comes from Karakhanid یَشِلْ, from Proto-Turkic yāĺïl — green.

Ancestry of “یاشیل”, step by step

Step	Language	Word	Meaning
1	Karakhanid	یَشِلْ	—
2	Proto-Turkic	yāĺïl	green