Except...I can.
As I cleaned the bathroom this morning, "Istanbul" by They Might Be Giants came up on my playlist. Of course the lyrics talk about how Istanbul was once Constantinople and how New York was once called New Amsterdam. After pondering the changes, they simply shrug them off stating that "people just liked it better that way."
Historically speaking, what is now Istanbul was founded as Byzantium circa 660 BC. As one might guess, it became the hub of the Byzantine empire, but more on that later. In about 330 AD, Constantine, the Holy Roman Emperor, seized Byzantium and named it the eastern capital of the Holy Roman Empire and renamed it Constantinople - after himself, like all good rulers of that era.
The change to Istanbul came after the fall of the Holy Roman Empire and when Constantinople fell to the Ottoman Empire. Of course all signs of the Christian faith were flushed out of the city, including the conversion of the cathedral Hagia Sofia into a mosque. (Interesting aside here - the Hagia Sofia, while still technically a mosque, serves as a museum where the carpets were removed and the plaster used to cover up the Christian themed mosaics were removed by expert restorers to show the basilica's original magnificence.) Naturally the name of the Holy Roman Emperor had to go, though the exact reason why it was renamed Istanbul remains a bit of a mystery. Needless to say, theories abound, each as plausible as the next.
Continuing on with the lyrics, the mention of the change from New Amsterdam to New York is a bit more relevant to anyone who lives here in the US. As most people should know (and if you don't, shame on you), the Dutch purchased the island of Manhattan for roughly sixty guilders (about $1000 in today's currency) from the Lenape tribe. They set up their farms and town (named, quite predictably, New Amsterdam) on the island and surrounding areas, and many of the Burroughs retain the names of the Dutch who originally settled them (so in case you were wondering, the original spelling of Bronx is actually Broncks). Anyway, in 1664, the English sailed into New York Harbor and pointed their guns at New Amsterdam and requested that they turn over control of the city to them. Peter Stuyvesant (the original Peg-Leg Pete) was quite adamant about keeping the British out, until the higher ups explained that New Amsterdam would be handed over to the British and that they would allow the Dutch to remain on their land. Now that New Amsterdam was in British control, a new name was needed, so it was named in the honor of the Duke of York and Albany (so, in case you're completely oblivious, that's why the state is called New York and the capital is called Albany - you may now kick ass on trivia game shows) and the brother of king-at-the-time Charles II.
Really, it's not like a quick query into the internet won't fetch the answers if you're really curious as to why it's now Istanbul and not Constantinople (or Byzantium, if you REALLY want to go back) or why Old New York was once New Amsterdam. As a history of student (and spending half a semester just on the history of New York City) I've had plenty of time to go diving into the how and why these cities had their names changed. Few cities retain their original names (though Moscow comes to mind, but oh, those crazy Russians - plus that's probably an entire entry by itself), and there's NEVER just some frivolous reason to change a city's name.