Who invented the erhu?

The earliest evidence of the erhu dates back to the 9th century during the Tang Dynasty when the instrument was called xiru (奚琴; simplified Chinese; 奚族 or 奚人, "Xi ethnic group"). It is believed to have been invented by a musician from the Xi people of the Khitans. By the 14th century, it was called the erxian (二弦, two strings).