the shield knot

The shield knot is believed to a universal symbol of protection which originated thousands of years ago.
This symbol is believed to be an ancient celtic symbol (celtic people were considered to be ancient people of Europe). It was used to ward off evil spirits. Celtic symbols were extensively used in jewelry and art and such patterns weren't derived from the nature. It is also thought to be the origin of the "Qabbalistic Cross" ritual. Some of the other names of this symbol are St.Hans cross and the Earth Square.