The erhu can be traced back to proto-Mongolic instruments which first appeared in China during the Tang dynasty. It is believed to have evolved from the xiqin (奚琴). The xiqin is believed to have originated from the Xi people located in current northeast China.
The first Chinese character of the name of the instrument (二, èr, 'two') is believed to come from the fact that it has two strings. An alternate explanation states that it comes from the fact that it is the second-highest huqin in pitch to the gaohu in the modern Chinese orchestra. The second character (胡, hú) indicates that it is a member of the huqin family, with hu commonly translated to mean 'barbarians'. The name huqin literally means 'instrument of the Hu peoples', suggesting that the instrument may have originated from regions to the north or west of China generally inhabited by nomadic people on the extremities of past Chinese kingdoms.
For most of history, the erhu was mostly a folk instrument used in southern China, whereas the sihu was preferred among northern musicians. However, in the 1920s, Liu Tianhua introduced the erhu to Beijing, and since, it has become the most popular of the huqin.