The English word Tibet, like the word for Tibet in most European languages, is derived from the Arabic word Tubbat. This word is derived via Persian from the Turkic word Töbäd (plural of Töbän), meaning "the heights". In Medieval Chinese, 吐蕃 (pronounced tǔfān), is derived from the same Turkic word. 吐蕃 was pronounced /t'o-bwǝn/ in Medieval times.

The exact derivation of the name is, however, unclear. Some scholars believe that the named derived from that of a people who lived in the region of northeastern Tibet and were referred to as Töbüt or Tübüt. This was the form adapted by the Muslim writers who rendered it Tübbett, Tibbat, etc., from as early as the 9th century, and it then entered European languages from the reports of the medieval European accounts of Piano-Carpini, Rubruck, Marco Polo and the Capuchin monk Francesco della Penna.

PRC scholars favor the theory that "Tibet" is derived from tǔfān.

 via