Jewish tradition states that the Magen David's (Star of David, Shield of David) six sides represent the shape of the shield that David used in battle.
The Shield of David is not mentioned in ancient rabbinic literature
A popular folk tale etymologyhas it that the Star of David is literally modeled after the shield of the young Israelite warrior David, who would later become King David. In order to save metal, the shield was not made of metal but of leather spanned across the simplest metal frame that would hold the round shield: two interlocking triangles. No reliable historical evidence for this etymology exists; this theory is refuted by a credible tradition that there was a Menorah engraved upon the shield which King David used in wartime. [1]
The earliest Jewish literary source which mentions the "Shield of David" is the Eshkol Ha-Kofer by Judah Hadassi from the middle of the 12th century CE
It is also said that David used this symbol as a euphemism for god.
If this is so, then I wonder what god he was actually promoting?
It appears that this symbol was used long before David adopted it.
This symbol was used in Brahmanism 6th - 2nd century BCE and then later in Hinduism from 2nd century BCE to 4th century CE.
Satkona Yantra cut into black stone with the diagram of the Kataragama deity. It is in the Museum fur Volkerkunde, Basel.