How did Istanbul get it's name? Why Istanbul? Why not something else?

Question:

How did Istanbul get it's name? Why Istanbul? Why not something else?

I know Istanbul was originally named Constantinople after Constantine, but I have not been able to find why the Turks chose the name Istanbul. Thanks for any help.

Best Answer - Chosen by Asker: According to an opinion that has existed for many years. the Byzantines did not refer to the city by its actual name, but, because of its size, simply as 'Polls' (the City), and when they wanted to say 'to the City', they sajd 'eist enpolin' (is-tin-polin), which was the origin of the name 'Istanbul'.