Japanese motifs -- tomoe

I had always thought of this motif as whirling commas and in fact, it represents a whirlpool in water.   My dictionary defines tomoe as a whirl  or eddy.

This symbol is used as protection from fire.  You can see it on roof tiles and other places for fire protection.

In Heian times, the Saionji family used it on thier carriage.

During the Kamakura period, it became a popular design motif for garments, household objects, and military items. 

Later, it was made into the mon or crest of the Hachiman shrine and represented thad God of War.