The city of Constantinople was founded in AD 324 from ancient Byzantium, by the Roman Emperor Constantine the Great, as the new capital of his empire. It was dedicated on 11 May, AD 330. Constantine chose to call it New Rome, but after his death it became known as Constantinople in his honour.
The name Istanbul comes from a Greek phrase meaning "into the city". It was used in Turkish from the 10th century; during Ottoman rule (from 1453), it continued to be used colloquially although the authorities often preferred Kostantiniyye (the Turkish version of Constantinople). The name Constantinople also persisted in the West, but some began to use Stamboul, a variant of Istanbul meaning "the city" (rather than "in the city").
The Turkish alphabet was changed from Arabic to Latin script in 1928, as part of the 1920s Turkification movement. After that, Turkey began to urge other countries to use Turkish names for its cities, instead of the transliterations to Latin script that had been used in the Ottoman times. The name Istanbul was officially adopted in 1930, and in time, most world languages came to use this name (or equivalent).
© Haydn Thompson 2017