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Imperial, royal and noble ranks in West, Central, South Asia and North Africa Emperor: Caliph · King of Kings · Shahanshah · Padishah · Sultan of Sultans · Chakravarti · Chhatrapati · Samrat · Khagan High King: Great King · Sultan · Maharaja · Beg Khan · Amir al-umara · Khagan Bek · Nawab King: Malik · Emir · Hakim · Sharif · Shah · Shirvanshah · Raja · Khan · Dey · Nizam · Nawab Grand Duke: Khedive · Nawab · Wāli · Yabghu
Khan (/kɑːn/) is a historic title of uncertain origin used in some medieval Central Asian societies to refer to a ruler or military leader. In the Seljuk Empire, it was the highest noble title, ranking above malik (king) and emir. In the Mongol Empire it signified the ruler of a horde (ulus), while the ruler of all the Mongols was the khagan or great khan. The title subsequently declined in importance. In Safavid Persia it was the title of a provincial governor, and in Mughal India it was a high noble rank restricted to courtiers.
After the downfall of the Mughals it was used promiscuously and became a surname
The origin of the term is disputed and unknown, possibly a loanword from the Ruanruan language. According to Vovin (2007, 2010) the term comes from qaγan (meaning emperor or supreme ruler) and was later used in several languages, especially in Turkic and Mongolic.
"Khan" is first encountered as a title in the Xianbei confederation for their chief between 283 and 289.[However, Russian linguist Alexander Vovin (2007) believes that the term qaγan originated among the Yeniseian-speaking Xiongnu people, and then diffused across language families. Subsequently, the Göktürks adopted the title and brought it to the rest of Asia. In the middle of the sixth century the Iranians knew of a "Kagan – King of the Turks".The Rourans may have been the first people who used the titles khagan and khan for their emperors.
Originally khans headed only relatively minor tribal entities, generally in or near the vast Mongolian and North Chinese steppe, the scene of an almost endless procession of nomadic people riding out into the history of the neighbouring sedentary regions. Some managed to establish principalities of some importance for a while, as their military might repeatedly proved a serious threat to such empires as China and kingdoms in Central Asia