The Triskel is an ancient Celtic symbol representing all trinities.
Three is seen as a magical number by many ancient cultures, especially
the Celts. Many of their gods appeared in triple-form. One belief is
that doing something thrice makes it so. In numerology, three
represents creative power and gheshtalt (when two things become more
than the sum of their parts).
As a Celtic symbol, the triskelion, usually consisting of spirals, but
also the "horned triskelion", sometimes plays a role in Celtic groups
and, rarely, can be seen in use by Germanic neopagan groups. The spiral
triskelion is one of the primary symbols of Celtic Re-constructionist
Paganism, and also used by some Wiccans. Celtic Re-constructionists use
the symbol to represent a variety of triplicates in their cosmology and
theology; it is also a favored symbol due to its association with the
god Manannán Mac Lir. Wicca is syncretic in nature and often
aesthetically adopts symbolism from various cultures, particularly
Celtic symbolism. It is less commonly used amongst Germanic neopagan
groups due to the non-Germanic origins of the symbol; use by Germanic
groups may be due to confusion or association with Norse symbols with
triple symmetries, like the Valknut, the Triquetra, or the symbol found
on the Snoldelev Stone.