The Suebian knot (German: Suebenknoten) is a historical male hairstyle ascribed to the tribe of the Germanic Suebi. The knot is attested by Tacitus in his 1st century AD work Germania, found on art by and depictions of the Germanic peoples, and worn by bog bodies.
According to Germania by Tacitus, the Suebian warriors combed their hair back or sideways and tied it into a knot, allegedly with the purpose of appearing taller and more awe-inspiring on the battlefield. Tacitus also reports that the fashion had spread to neighboring Germanic tribes among the younger warriors, while among the Suebians, the knot was sported even by old men as a status symbol, which "distinguishes the freeman from the slave", with the most artful knots worn by the most wealthy nobles.
Suebian knots were found to be worn by a number of bog bodies:
The hair is divided at the back in two uniform strands, slicked and laid in opposite directions around the head. On one side of the head, usually in the temporal region, the two strands are individually tightened in the same direction. The two strands are then twisted, whereby the rotation of the two individual strands loosens somewhat. A loop is formed from the resulting braid and the excess braid end is put in a loop through the loop. By natural untwisting the resulting knot tightens and stops without further aids. 
The Osterby Man had an incipient vertex balding and very long and thin hair. Experimental archaeological wearing tests with this hairstyle showed that the node just as well holds only at very long and thin hair, as in the bog body.  A certain amount of hair grease improves also the durability of the hairstyle. Strong and full hair is attributed to the decline in abundance of this hairstyle.
Hair of bog body Dätgen Man (Germany)
A Roman bronze figurine depicting a kneeling Germanic man adorned with a Suebian knot Bibliothèque nationale de France
German at Wien Museum
Portonaccio sarcophagus (Man on the lower right side)
Terra cotta mask at British Museum
Captive with Suebian knot National Museum of Romanian History
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