The triquetra is an ancient Celtic symbol of three intertwined circles.  It was probably first associated with early Celtic goddesses and their domains: earth, ocean and sky.  But the exact meaning was lost a long time ago. 

This complex and intricate symbol can be found on ancient carvings and manuscripts found in Celtic monasteries. In most people’s minds, it represents Irish heritage and/or Celtic roots. It makes us think of druids and the folklore attached to the Celtic people. 

There are quite a few places where you can find Celtic knot work on anything from coffee cups to jewelry and chances are, those places will tell you one Celtic knot means this and one Celtic knot means that but the reality is, the ancient meaning was lost a long time ago. So take the meanings you find on websites and in stores with a grain of salt, as they might just be put there to get you to buy the product.

In Latin, the word triquetra means three cornered.  There are many different interpretations of this symbol but all are intricate, interlocking circles. Some of them are authentic and some are a modern take on this archaic symbol.  More than likely, the interlocking symbols represented the Celtic view that life was constantly ebbing and flowing but always coming back around, full circle.  

Christians adopted the triquetra as a symbol for the Father, the Son and the Holy Spirit or Ghost.  The triquetra was used on the 1611 edition of the King James Bible.  It may have been used as a sort of talisman, in early Christian times,  to keep away evil or it may have been used as just a decoration.  No one really knows what the true meaning was.

Christians are not the only ones who have used the triquetra as a symbol of their belief system.  Wiccans and Neopagans also have adopted the symbol. It means a variety of things for Wiccans and Neopagans but most people will go with the maiden, mother and crone representation.

Whatever the mindset of a person is, more than likely, the triquetra will represent the way all things are connected and how all things are bound together in life. And whatever your religious views are, the idea of all things working together to create harmony and balance is a good thought and showing that thought through the triquetra symbol is beautiful thing.

Source-
The Everything Celtic Wisdom Book, by Jennifer Emick