palladium

plural palladia

1. A safeguard.

   The trial by jury is the Palladium of our civil rights.

   1765–1769, William Blackstone, Commentaries on the Laws of England, (please specify |book=I to IV), Oxford, Oxfordshire: […] Clarendon Press, →OCLC

   2 more examples

   [H]ow unspeakably ominous to dim Royalist participators; for whom Royalism was Mankind's palladium[.]

   1837, Thomas Carlyle, The French Revolution: A History […], volume (please specify |volume=I to III), London: Chapman and Hall, →OCLC, (please specify the book or page number)

   The presupposition of the Prometheus myth is to be found in the extravagant value which a naive humanity attached to fire as the true palladium of every ascending culture.

   1967, Friedrich Nietzsche, translated by Walter Kaufman, The Birth of Tragedy, published 1872, in 1967

plural palladiums

1. countableuncountableA chemical element (symbol Pd) with an atomic number of 46: a rare, lustrous silvery-white metal.
2. countableA single atom of this element.

alternative Palladion

1. human sciencesA wooden statue of great antiquity on which the safety of Troy and later Rome was said to depend.