Prussia (region)
Prussia (Old Prussian: "Prūsa"; ; ; ; ) is a historical region in Europe, stretching from Gdańsk Bay to the end of Curonian Spit on the southeastern coast of the Baltic Sea, and extending inland as far as Masuria. The territory and inhabitants were described by Tacitus in Germania in  98, where Suebi, Goths and other Germanic people lived on both sides of the Vistula River, adjacent to the Aesti (further east). About 800 to 900 years later the Aesti were named Old Prussians, who, since 997, repeatedly defended themselves against take-over attempts by the newly created Duchy of the Polans. The territory of the Old Prussians and neighboring Curonians and Livonians was unified politically in the 1230s as the State of the Teutonic Order. Prussia was politically divided between 1466 and 1772, with western Prussia under protection of the Crown of Poland and eastern Prussia a Polish–Lithuanian fief until 1660. The unity of both parts of Prussia remained preserved by retaining its borders, citizenship and autonomy until western and eastern Prussia were also politically reunited under the German Kingdom of Prussia (which despite the name was based in Berlin, Brandenburg). It is famous for many lakes, as well as forests and hills. Since the military conquest of the area by the Soviet Army in 1945 and the expulsion of the German-speaking inhabitants it was divided between northern Poland (most of the Warmian-Masurian Voivodeship), Russia's Kaliningrad exclave, and southwestern Lithuania (Klaipėda Region). The former German kingdom and later state of Prussia (1701–1947) derived its name from the region.
Prussia (region)
The area was settled by the bearers of the Corded Ware culture in the 4th millennium . These were presumably the early Indo-European speakers, which in the Baltic would diversify into the satem Balto-Slavic branch which would ultimately give rise to the Balts as the speakers of the Baltic languages. The Balts would have become differentiated into Western and Eastern Balts in the late 1st millennium . The region was inhabited by ancestors of Western Balts – Old Prussians, Sudovians/Jotvingians, Scalvians, Nadruvians, and Curonians while the eastern Balts settled in what is now Lithuania, Latvia and Belarus.
Aesti
The Aesti (also Aestii, Astui or Aests) were an ancient people first described by the Roman historian Tacitus in his treatise "Germania" (circa 98 AD). According to Tacitus, the territory of Aesti was located somewhere east of the "Suiones" (Swedes).
Aesti
According to Tacitus, the Aesti had the same customs and attire as the Germanic Suevi. It has been suggested that the Aesti worshipped the mother of the gods, similar to the Nerthus cult among northern Germanic peoples. Tacitus wrote that the Aesti were ""the only people who collect amber—"glaesum" is their own word for it—in the shallows or even on the beach"".

Question: Prussia is a historical region stretching from Gdańsk Bay to the end of Curonian Spit on the southeastern coast of the Baltic Sea, and extending inland as far as Masuria, Suebi, Goths and other Germanic people lived on both sides of the Vistula River, adjacent to which ancient people first described by the Roman historian Tacitus in his treatise "Germania" (circa 98 CE)?
Answer: Aesti