One of the most obscure branches of the Indo-European language group is the Tocharian branch. The two languages Tocharian A and Tocharian B that made up this group have both been long extinct.
Both languages were once spoken in eastern Asia, to the northwest of China. Chinese records of the time mention this group of nomadic barbarians.
The Tocharian languages are a major geographic exception to Indo-European branches in that they are the only one that spread directly east from the theoretical Indo-European starting point in southern Russia.