pelopium

from The Collaborative International Dictionary of English v.0.48

Pelopium \Pe*lo"pi*um\, n. [NL., fr. L. Pelops, brother of
   Niobe, Gr. ?.] (Chem.)
   A supposed new metal found in columbite, afterwards shown to
   be identical with columbium, or niobium.
   [1913 Webster]