grot vs lava

grot

noun
  • A grotto. 

  • A miserable person. 

  • Any unpleasant substance or material. 

lava

noun
  • Magma. 

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

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

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