Where does “مهدیقلی” come from?

مهدیقلی (Persian) comes from Urdu قلی, from Proto-Turkic kül — ash.

Ancestry of “مهدیقلی”, step by step

Step	Language	Word	Meaning
1	Urdu	قلی	slave; laborer; coolie
2	Proto-Turkic	kül	ash