Triquetra is a noun derived from the Latin tri- ("three") and quetrus ("cornered").
Its original meaning ws simply "triangle" and it has been used to refer to various three-cornered shapes.
Nowadays, it has come to refer exclusively to a particular more complicated shape formed of three vesicae piscis, somtimes with an added cicle in or around it,
This has been used as a religious symbol of things and persons that are threefold.
The triquetra has been found on runestones in Northern Europe and on early Germanic coins. It presumably had pagan religious meaning and it bears a resemblance to the Valknut, a symbol associated with Odin.
(This is expecially interesting for me, an old Kraut myself.)
The Trinity Knot holds major significance in Irish Celtic mythology in that it is believed to represent the three stages of woman (Maiden/Wife, Mother, and Crone (old woman).
In contemporary Ireland, It is traditional for a man to give a loved one a trinket such as a necklace or ring signifying his affection towards her. It is believed to represent the three promises of a relationship such as to love, honour, and protect. It is common for the design of the Trinity Knot to be engraved on a wedding ring and attaches to a Claddagh ring
(another Irish traditional ring given for friendship or engagement)
Germanic Neopagan groups who use the triquetra to symbolize their faith generally believe it is originally of Norse and Germanic origins.
The symbol is also sometimes used by Wiccans and some NewAgers to symbolize either the Wiccan triple goddess or the interconnected parts of our existence (Mind, Body, and Soul).
Also the triquetra is a symbol of protection in the Wiccan religion. It is also said to represent family; Father, Mother and Child.
It is difficult to date the exact origin of the Celtic triquetra, and whether it was first used in a Christian or pagan context; the distinctive interlace/knotwork artistic style did not fully develop until ca. the seventh century A.D., but the triquetra is the simplest possible knot.
~ Blessed Be ~