The following winter (this was the year in which Cn. Pompey and M. Crassus were consuls), those Germans [called] the Usipetes, and likewise the Tenchtheri, with a great number of men, crossed the Rhine, not far from the place at which that river discharges itself into the sea. The motive for crossing [that river] was, that having been for several years harassed by the Suevi, they were constantly engaged in war, and hindered from the pursuits of agriculture. The nation of the Suevi is by far the largest and the most warlike nation of all the Germans. They are said to possess a hundred cantons, from each of which they yearly send from their territories for the purpose of war a thousand armed men: the others who remain at home, maintain [both] themselves and those-engaged in the expedition. The latter again, in their turn, are in arms the year after: the former remain at home. Thus neither husbandry, nor the art and practice of war are neglected. But among them there exists no private and separate land; nor are they permitted to remain more than one year in one place for the purpose of residence. They do not live much on corn, but subsist for the most part on milk and flesh, and are much [engaged] in hunting; which circumstance must, by the nature of their food, and by their daily exercise and the freedom of their life (for having from boyhood been accustomed to no employment, or discipline, they do nothing at all contrary to their inclination), both promote their strength and render them men of vast stature of body. And to such a habit have they brought themselves, that even in the coldest parts they wear no clothing whatever except skins, by reason of the scantiness of which, a great portion of their body is bare, and besides they bathe in open rivers.
Julius Caesar, The Gallic Wars, Book IV, Ch 1 (58–49 BC)