Actually, the triquetra is connected to all of the above – as well as to Christianity.
The triquetra is derived from the Celts where it is also known as a “trinity knot”. The Symbol Dictionary says it predates Christianity and was likely a Celtic symbol of the Goddess or the god Odin.
When the Celts became Christian, the symbol was used to represent God in the three Persons of the Trinity. A triquetra comprised of interlaced fish is one of the earliest known symbols of Christianty which was found in a Roman catacomb. In fact, each branch of the triquetra is actually in the shape of a fish which has long been used to represent Christianity.
Use of triquetra to symbolize the Trinity is one of the most common uses of the symbol today.
However, it is also used by Wiccans and neopagans. For them, the triquetra symbolizes the triple aspects of the goddess (maid, mother, crone). According to Wiccan Teachings on Facebook, “the Celts worshiped a moon goddess who was a trio goddess. She was associated with the three lunar phases; when the moon was waxing, waning, and full. It represents the three stages of life – young, adult, old – and the three stages of life – birth, life, death. It can also be used to denote the mind, body and soul connection, or to denote the three domains of earth according to Celtic mythology – earth, sea and sky.
An upside-down version of the triquetra is also associated with Celtic Christianity. However, it is also used to symbolize the upending of the Truth (such as in an upside-down cross) and a symbol of the beast.