Where does “Ыстанбул” come from?

Ыстанбул (Kyrgyz) comes from Turkish İstanbul, from Byzantine Greek πόλις, from Proto-Hellenic ptólis, from Proto-Indo-European tpólHis, from Proto-Indo-European tpelH- — fortification, city.

Ancestry of “Ыстанбул”, step by step

StepLanguageWordMeaning
1TurkishİstanbulIstanbul
2Byzantine Greekπόλιςin the City; city; a whole country, as dependent...
3Proto-Hellenicptóliscity
4Proto-Indo-EuropeantpólHis—
5Proto-Indo-EuropeantpelH-fortification, city
Every word from Proto-Indo-European tpelH- →Every word from Proto-Indo-European tpólHis →Every word from Proto-Hellenic ptólis →