On the Antiquities of Prussia

...entered the region of the Borussii, a people who, according to Ptolemy, had their settlements near the Riphean mountains—where they extend more widely toward the north, and not far from where the Tanais erupts from them—and who, driven by their own misfortune (for the earth there is rigid with perpetual snows and chills, and is condemned to every ministry of nature), left their fatherland to seize new seats and fell into these places. Because both the fertility of the soil and the pleasantness of the pastures and lakes pleased them when they first arrived, and they progressed no further, they chose these seats for themselves by unanimous consent. And so that they might last forever for their descendants, they called the land by their ancestral name, Borussia, which even today is commonly called Brussia by the dropping of a single letter. This is the true origin of this people. And as for the rest of what is said, I judge it to be regarded as nothing more than an old wives' tale. He provides the greatest evidence for this matter in the fact that, even to this day, the peoples living near the Ripheans use the same language as these people. Once their settlements were established, the Borussii easily occupied the land, which was vacant of cultivators (for the Goths had left it in large numbers), with no one opposing them, apart from that portion which is by the Vistula. This was still held by a very few Germans. Therefore, extending themselves from the Chronus river as far as the territory of the Hulmigeri—a name which, after the ancient colonists were driven out by the Goths, had begun to be applied to the middle of this coastal region—they obscured the names of the others living here with their own name in a short time. This perhaps happened because the Borussii were better known to the bordering peoples, such as the Germans...