from Wikipedia Tashkent:
Tashkent (Uzbek: Toshkent, Тошкент; Russian: Ташкент, Turkish: Taşkent) is the capital of Uzbekistan and also of the Tashkent Province. The officially registered population of the city in 2006 was 2.1 million. According to unofficial data, the population is more than 3 million.
In medieval times the town and the province were known as "Chach". Later, the town came to be known as Chachkand/Chashkand, meaning "Chach City." (Tash in Turkic language means stone. Kand, qand, kent, kad, kath, kud--all meaning a city, are derived from the Sogdian, kanda, meaning a town or a city. They are found in city names like Samarkand, Yarkand, Penjikent etc.).
After the 16th century, the name was steadily changed slightly from Chachkand/Chashkand to Tashkand, which, as "stone city", was more meaningful to the new inhabitants than the old name. The modern spelling of Tashkent reflects Russian orthography.