The emblem of the Celtic trinity, along with the Celtic knot, was one of the most popular among the Celts. It was called the Triquetra, which is one strand bound within itself to form three loops in one individual motif. No one is exactly sure what the Celtic trinity emblem represented. However, the Triquetra in Celtic symolism denoted threefold, such as the soul, mind and heart or past, present and future. It was conceived that the Germanic culture had adopted the Celtic Trinity symbol. Triquetra comes from the Latin word tri which means 'three' and quetrus, which stands for 'corners'. The Triquetra symbol was customarily used on ancient Germanic coins and rune stones. It also has a faint likeness to the Norse god, Odin's, emblem, Valknut.
The earliest symbols of the trinity came about for ornamental uses as well as for filling in space. You can find this is one of the most popular of the oldest works, "The Book of Kells" which is embedded with the Celtic Trinity symbol. It wasn't until later years that the Christians adapted the Celtic Trinity symbol to use as the meaning of the Holy Trinity, which is God the Father, God the Son and God the Holy Spirit.
The Celtic Trinity has become popular in present times. John Paul Jones, a huge rock idol from the legendary band, Led Zeppelin always used the Triquetra for his personal emblem. He most likely used it to display his Celtic heritage. The Celtic Trinity symbol has also been seen on many popular television shows, including the TV show, Charmed whereby it meant the three witches' power as one entity. The Triquetra also known as the Celtic Trinity is widely used today, especially by those of Celtic heritage.