In 1453, Ottoman Sultan Mehmed II conquered the city and made it the capital of the Ottoman Empire. Now under new rule, the metropolis was dubbed "Istanbul" from the Greek phrase "eis ten polin," which meant "in the city." The name of the city wasn't officially changed until 1930, and Westerners continued to refer to it as Constantinople on maps and in speech into the '60s.

Why they changed it, I can't say. People just liked it better that way. Why did Constantinople get the works? That's nobody's business but the Turk's.

The story is not simple, because there were diverse civilisations there and it depends who gave the name. Remember that is had also other names before, such as Byzance. 1) Constantinople ("City of Constantine"): "It remained the principal official name of the city throughout the Byzantine period, and the most common name used for it in the West until the early 20th century." Other Byzantine names: - "Queen of Cities" (Βασιλίς τῶν πÏŒλεων). - The City (Greek: hÄ“ Polis, ἡ ΠÏŒλις, Modern Greek: i Poli, η ΠÏŒλη). (the source of the later Turkish name, Istanbul) 2) "Kostantiniyye (Arabic القسطنطينية, al-Qusá¹­aná¹­iniyah, Ottoman Turkish قسطنطينيه Kostantiniyye) is the name by which the city came to be known in the Islamic world. It is an Arabic calqued form of Constantinople, with an Arabic ending meaning 'place of' instead of the Greek element -polis. After the Ottoman conquest of 1453, it was used as the most formal official name in Ottoman Turkish, and remained in use throughout most of the time up to the fall of the empire in 1923." 3) "The modern Turkish name Ä°stanbul (IPA: [istambul] or colloquial [ɨstanbul]) is attested (in a range of different variants) since the 10th century, at first in Armenian and Arabic and then in Turkish sources." "Ä°stanbul was the common name for the city in normal speech in Turkish even since before the conquest of 1453, but in official use by the Ottoman authorities, other names such as Kostantiniyye were preferred in certain contexts." "After the creation of the Turkish Republic in 1923, the various alternative names besides Ä°stanbul became obsolete in Turkish. In an edict of March 28, 1930, the Turkish authorities officially requested foreigners to cease referring to the city with their traditional non-Turkish names (such as Constantinople) and to adopt Ä°stanbul as the sole name also in the foreign languages." These are just some of many names of this city. These are presentend in an interesting article, which I largely used in the quotes: http://en.wikipedia.org/wiki/Names_of_Istanbul