midden vs refuse heap

midden

noun
  • A shelter made of vegetation and other materials by packrats. 

  • An accumulation of dried urine and fecal deposits made by hyraxes. 

  • A refuse heap usually near a dwelling. 

  • A prehistoric pile of bones and shells. 

  • A dungheap. 

refuse heap

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