>>211890597 (OP)It’s not called that in any of the languages I speak, nor locally. So that’s why.
>the Greek wayMany people believe that the name Istanbul is actually derived from a Greek phrase (this is contested, but it doesn’t come from any obvious Turkic root). There’s old Greek influence all over Turkey, including in the modern language. The Greeks (and Armenians and others) were in Asia Minor centuries ahead of the Seljuks.