2 October 2009
Palladium, element 46, was discovered in 1803 by British chemist William Wollaston, who named it after the recently discovered asteroid Pallas. Wollaston writes in the Philosophical Transactions of the Royal Society in 1805:
I [...] subsequently obtained another metal, to which I gave the name Palladium, from the planet that had been discovered nearly at the same time by Dr. Olbers.
The asteroid is named after the Greek goddess Athena, or Pallas Athene, in Greek Παλλας. Wollaston used the Latin adjective Palladius, referring to things related to Athena, as the basis for the elemental name, hence the d. Compare it to cerium, element 58, discovered at about the same time, which is named for the asteroid Ceres.
Palladium has the chemical symbol Pd.
Sources:
Oxford English Dictionary, palladium, 3rd Edition, December 2007.
Oxford English Dictionary, Palladian, adj.1, 3rd Edition, September 2008.