The Suebian knot was a hairstyle worn in the 1st century by young men of the Suebians, a Germanic tribe. (and apparently later since the knot was preserved in the coat of arms of Østerby)
Allegedly it is supposed to make the wearer look taller and more formidable, but I think it just makes the wearer look more adorable.
(Source: theslavbarbarian)