Triquetra

Triquetra (/traɪˈkwɛtrə/; Latin tri- "three" and quetrus "cornered") originally meant "triangle" and was used to refer to various three-cornered shapes. It has come to refer exclusively to a particular more complicated shape formed of three vesicae piscis, sometimes with an added circle in or around it. Also known as a "trinity knot", the design is used as a religious symbol adapted from ancient Celtic images by Christianity. It is similar to Odin's symbol, the valknut.