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Indeed, the Turkish name for the city (Istanbul) is itself emblematic of the huge significance of the place for trade purposes even when the Byzantines and Ottomans were at each others' throats. Istanbul is derived from a Turkish phrase which roughly translates as "into the city." When people asked each other where they were going, if the destination was Constantinople they would simply say "into the city."

Well Ottomans actually paraphrased the Byzantine Greek epxression Eis tin Polin (Είς τήν Πόλιν) which means rougly In the City, which is the answer to the question of the Ottomans: Where am I? Answer: Eis tin Polin. That answer sounded in the Ottoman ears something like (Eis) Is- (tin) tan- (Poli) bul.


That was because Constantinople was so massively important to the region, that you didn't need to even name it. Just calling it "the city" was enough to let everyone know what you meant.
agree with this since everyhting around Constantinople was considered rural area so the only urban area which could called City was Constantinople. Even nowadays Greeks call Constaninople Polis which means city