litter box vs midden

litter box

noun
  • A box used to provide a soiling area for (usually) pet cats, generally filled with kitty litter, sand, clay chips, etc. 

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. 

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