Palladium

Part of speech: noun (n.)

1. Any statue of the goddess Pallas; esp., the famous statue on the preservation of which depended the safety of ancient Troy.

2. Hence: That which affords effectual protection or security; a sateguard; as, the trial by jury is the palladium of our civil rights. Blackstone.

Part of speech: noun (n.)

A rare metallic element of the light platinum group, found native, and also alloyed with platinum and gold. It is a silver-white metal resembling platinum, and like it permanent and untarnished in the air, but is more easily fusible. It is unique in its power of occluding hydrogen, which it does to the extent of nearly a thousand volumes, forming the alloy Pd2H. It is used for graduated circles and verniers, for plating certain silver goods, and somewhat in dentistry. It was so named in 1804 by Wollaston from the asteroid Pallas, which was discovered in 1802. Symbol Pd. Atomic weight, 106.2.