The triquetra, also known as a "trinity knot," is believed to represent the three promises of a relationship such as to love, honour, and protect, and can be found as a design element on Claddaghs and other wedding or engagement rings.
Perfect promise ring. Anniversary ring. Shanore Celtic Trinity knot ring in sterling silver. Celtic Trinity knots are an Ancient Celtic symbol as well as a Christian symbol. They frequently represent a sacred three; either father, son, holy spirit, or mother, maiden, crone. It also represents unity and wisdom.