Etymology of Ouroboros, the Infinity Symbol:
 Known as the oldest allegorical symbol in alchemy in ancient Egypt, Ouroboros expresses the unity of all things, material and spiritual, which never disappear but perpetually change form in an eternal cycle of destruction and re-creation. represents the concept of eternity and endless return as the lower part of the symbol showcases the destructive force of nature, night, earth and even Yin while the upper half represents the generation and creative force, day, heaven & yang. The term ouroboros is derived from two words in ancient Greek language. The first word is “oura” which means “tail” and the second is “boros” which means “eating”. When we combine, these two words it gives the meaning “he that eats his own tail” or “tail eater”.  
A serpent eating its own tail has been depicted in different versions of the infinity symbol throughout the history. The snake eating its own tail simply represents the recreation of life through death by the universe. It is interpreted as some kind of a rebirth of the dead reaching an immortality. Therefore, it is assumed that the infinity symbol was derived from the original symbol of ouroboros.