litter box vs sandpit

litter box

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

sandpit

noun
  • A children’s play area consisting of a large container filled with sand. 

  • A place or pit from which sand is excavated. 

  • A small-scale illustrative model of the theater of war in the Middle East. 

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