Of all the gods, giants, beasts, and spirits that stalked the Viking mental landscape, Jörmungandr – the world-coiling serpent – remains one of the most renowned. Jörmungandr is also known as the Midgard Serpent because he was a sea monster so large that he wrapped all the way around Midgard (the world of humans). When this gigantic beast stirs, storms, earthquakes, and tidal waves erupt. Jörmungandr lies in the depths of the sea, encircling the earth, holding his own tail in his mouth, waiting for the day of Ragnarok. It is said that when the serpent releases his tail and begins his attack, Ragnarok – the ‘final’ dark day for the gods – will begin.
Jörmungandr is not the only world-coiling serpent across the thousands of years and hundreds of cultures that color the human imagination. In fact, the image of a tail-swallowing dragon can be found worldwide and throughout history. This symbol of the circular snake is called the ouroboros. The earliest known ouroboros depiction is from the grave of Pharaoh Tutankhamen from the 13th century B.C. Since that time, similar images have shown up in ancient Chinese, Persian, Hindu, Greek, and Mesoamerican sites and artifacts. The ouroboros was also prominently featured in the language of mysticism amongst the Gnostics, Hermetic, and alchemists throughout Late Antiquity and the Middle Ages.
In most of these settings, the ouroboros signifies time – depicting the living, breathing cycle of ages that have no real beginning and no real end. In Roman sources, the ouroboros symbolized the god Saturn (the Greek Kronos from where we get words like chronology and chronometer). Saturn/Kronos was a god of time. He was considered by the Greco-Romans to be especially savage and terrifying. He was lord of the Titans – spirits of elemental chaos that were something like the giants (Jötnar) of Viking lore. In all this imagery, the ouroboros represents the endless cycles of creation and destruction. In fact, many scholars believe that our mathematical symbol for eternity – the sideways figure eight (∞) – is a shorthand adaptation of the ouroboros symbol.
Source: Sons of Vikings