The triquetra is a Celtic knot with a triangular design symbolizing all trinities including the Triple Goddess (Maiden, Mother & Crone); the eternal cycle of life, death, and rebirth, and the realms of Air, Earth and Sea which, to the ancient Celts, represented the entire Universe.

To Christians, the triquetra has been used to symbolize the Holy Trinity (Father, Son & Holy Ghost)

In fact, many cultures and religions have considered the number three to be holy or divine for millennia. A symbol of three interlocking circles looking somewhat like a three-leaf clover without out stem has been found on religious statues in India that were made 5000 years ago.