Tacitus asserted that the Suevi were one of the tribes that claimed descent from one of the many sons of Mannus.

"To Mannus they assign three sons, from whose names, they say, the coast tribes are called Ingaevones; those of the interior, Herminones; all the rest, Istaevones. Some, with the freedom of conjecture permitted by antiquity, assert that the god had several descendants, and the nation several appellations, as Marsi, Gambrivii, Suevi, Vandilij, and that these are nine old names. "

He also states they sacrificed to Isis. This was probably a local goddess, but who she was we do not know. All we know is that she was associated with a ship. He then mentions the Suebi in some detail.

"I must now proceed to speak of the Suevians, who are not, like the Cattans and Tencterians, comprehended in a single people; but divided into several nations all bearing distinct names, though in general they are entitled Suevians, and occupy the larger share of Germany. This people are remarkable for a peculiar custom, that of twisting their hair and binding it up in a knot. It is thus the Suevians are distinguished from the other Germans, thus the free Suevians from their slaves. In other nations, whether from alliance of blood with the Suevians, or, as is usual, from imitation, this practice is also found, yet rarely, and never exceeds the years of youth. The Suevians, even when their hair is white through age, continue to raise it backwards in a manner stern and staring; and often tie it upon the top of their head only. That of their Princes, is more accurately disposed, and so far they study to appear agreeable and comely; but without any culpable intention. For by it, they mean not to make love or to incite it: they thus dress when proceeding to war, and deck their heads so as to add to their height and terror in the eyes of the enemy.

Of all the Suevians, the Semnones recount themselves to be the most ancient and most noble. The belief of their antiquity is confirmed by religious mysteries. At a stated time of the year, all the several people descended from the same stock, assemble by their deputies in a wood; consecrated by the idolatries of their forefathers, and by superstitious awe in times of old. There by publicly sacrificing a man, they begin the horrible solemnity of their barbarous worship. To this grove another sort of reverence is also paid. No one enters it otherwise than bound with ligatures, thence professing his subordination and meanness, and the power of the Deity there. If he fall down, he is not permitted to rise or be raised, but grovels along upon the ground. And of all their superstition, this is the drift and tendency; that from this place the nation drew their original, that here God, the supreme Governor of the world, resides, and that all things else whatsoever are subject to him and bound to obey him. The potent condition of the Semnones has increased their influence and authority, as they inhabit an hundred towns; and from the largeness of their community it comes, that they hold themselves for the head of the Suevians."

Tacitus states after that the Suebi lands stretch to the middle of Germany. We are then told somewhat later that, "For, Suevia is parted by a continual ridge of mountains; beyond which, live many distinct nations. "

From reading Germania, we are given the impression that the Suebi are a very powerful people that covered a great area of land. In some of this he may be mistaken as he lumps tribes that spoke a Northern dialect of Germanic with Eastern groups.

Note all translations are taken from www.fordham.edu/halsall/source/tacitus1.html