tellurian vs tellurium

tellurian

adj
  • Of a mineral: containing tellurium. 

  • Of or relating to the earth; (specifically, chiefly science fiction) inhabiting planet Earth as opposed to other planets. 

tellurium

noun
  • A single atom of this element. 

  • A variant spelling of tellurion. 

  • The chemical element with atomic number 52. Symbol: Te. A rare, brittle, mildly toxic, silver-white metalloid. 

How often have the words tellurian and tellurium occurred in a corpus of books? (source: Google Ngram Viewer )