Jordanes/Jordanis/Jornandes. Historia Gothorum (History of Goths, or Gothic History, or The Origin and Deeds of the Goths). Sixth Century AD (c AD 551):

Mierow, Charles Christopher, tr. The Gothic History of Jordanes: In English Version. Princeton: Princeton University Press, February, 1915.
https://ia802604.us.archive.org/28/items/gothichistoryofj00jorduoft/gothichistoryofj00jorduoft.pdf