θυρεός

Etymology
From.

Noun

 * 1) a stone put against a door to keep it shut, a door-stone
 * 2) a wide oblong shield (like a door), opp. to  (as Lat.  to )
 * 3) disk forming part of
 * 4)  oval

Noun

 * 1)  coat of arms, escutcheon