Bactrian language
They were first described by the Roman historian, Ammianus Marcellinus, who was in Bactria during 356–57 CE; he described the "Chionitæ" as living with the Kushans. Ammianus indicates that the Xionites had previously lived in Transoxiana and, after entering Bactria, became vassals of the Kushans, were influenced culturally by them and had adopted the Bactrian language. They had attacked the Sassanid Empire, but later (led by a chief named Grumbates), served as mercenaries in the Sassanian army.