Ceramic of man and cow from the Kingdom of Khotan 7th-9th C. CE

"The origin of the name "Hephthalites" is unknown, it may stem either from a Khotanese word *Hitala meaning "Strong", from hypothetical Sogdian *Heβtalīt, plural of *Heβtalak, or from postulated Middle Persian *haft āl "the Seven Al"

In the late 5th century CE they expanded eastward through the Pamir Mountains, which are comparatively easy to cross, as did the Kushans before them, due to the presence of convenient plateaus between high peaks. They occupied the western Tarim Basin (Kashgar and Khotan), taking control of the area from the Ruanruans, who had been collecting heavy tribute from the oasis cities, but were now weakening under the assaults of the Chinese Northern Wei dynasty. In 479 they took the east end of the Tarim Basin, around the region of Turfan.

When Khosrow I died in 579, the Hephthalites of Tokharistan and Khotan took advantage of the situation to rebel against the Sasanians, but their efforts were obliterated by the Turks." 

-taken from Wikipedia

Source:

https://commons.wikimedia.org/wiki/File:2015-13-101702_-_Hotan_Museum_-_Keramik_mit_Kuh-_und_Menschenkopf,_Tang_Dynastie.JPG

Quote:

https://en.wikipedia.org/wiki/Hephthalites