Lameen Souag at Jabal al-Lughat posts infrequently, but it’s always worth reading. Last month I meant to blog his post comparing the traditional (but probably erroneous) etymology of Istanbul < Greek εις την Πόλιν, pronounced /istimbóli(n)/ and meaning 'to the City,' with
‘usquuf, “bishop” in Arabic, which apparently derives from a Coptic reinterpretation of Greek episkopos “bishop” as e-pi-skopos “to the skopos“, due to which skopos was reanalyzed as meaning “bishop”.
I am unqualified to judge the validity of the latter etymology, but it’s certainly interesting.
And this month he has a post about one of the easternmost outposts of Berber, El-Fogaha (الفقهة) in central Libya, where some archaic Berber words are retained and there are some interesting phonological developments.
On Istanbul, the more commonly accepted explanation these days is that it’s derived directly from the Greek name Konstantinopolis, but as Pospelov says, there’s no actual evidence, and the forms are too divergent to allow us to simply assume the change. (The artificial Turkish form Islambol ‘filled with Islam’ is simply a folk etymology.)