dross vs lava

dross

noun
  • Residue that forms on the surface of molten metal from oxidation. 

  • Worthless or trivial matter. 

  • The impurities in metal. 

  • Waste or impure matter. 

  • A waste product from working with metal. 

verb
  • To remove dross from. 

lava

noun
  • The molten rock ejected by a volcano from its crater or fissured sides. 

  • Magma. 

  • A shade of red, named after the volcanic lava. 

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