A turban (from Persian دوربند, durband; via Middle French turbant) is a type of headwear based on cloth winding. Featuring many variations, it is worn as customary headwear by people of various cultures. Communities with prominent turban-wearing traditions can be found in the Indian subcontinent, Southeast Asia, the Arabian Peninsula, the Middle East, the Balkans, the Caucasus, Central Asia, North Africa, West Africa, East Africa, and amongst some Turkic peoples in Russia as well as Ashkenazi Jews. A keski is a type of turban, a long piece of cloth roughly half the length of a traditional "single turban", but not cut and sewn to make a double-width "Double Turban" (or Double Patti). Wearing turbans is common among Sikh men, and infrequently women. They are also worn by Hindu monks. The headgear also serves as a religious observance, including among Shia Muslims, who regard turban-wearing as Sunnah mu’akkadah (confirmed tradition). The turban is also the traditional headdress of Sufi scholars. Additionally, turbans have often been worn by nobility, regardless of religious background. The origins of turbans are uncertain. Some of the ancient civilizations such as those of Ancient India, Mesopotamia, Sumerian, and Babylonian evidently used turbans. A style of turban called a phakeolis continued to be worn in that region by soldiers of the Byzantine army in the period 400–600, as well as by Byzantine civilians as depicted in Greek frescoes from the 10th century in the province of Cappadocia in modern Turkey, where it was still worn by their Greek-speaking descendants in the early 20th century. The Islamic prophet, Muhammad, who lived 570–632, wore a turban. The style of turban he introduced was a cap with a cloth tied around it; this headwear is known as Imamah and was emulated by Muslim kings and scholars throughout history. Shiah clergies today wear white turbans unless they are descendants of prophet Muhammad or Sayyid, in which case they wear a black turban. Many Muslim men choose to wear green, because it represents paradise, especially among followers of Sufism.