leaf litter vs litter box

leaf litter

noun
  • Dead plant material, such as fallen leaves, bark, and twigs, that has fallen to the ground and may be used by animals as habitat or for nest-building, eventually decomposing and releasing nutrients into the soil. 

litter box

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

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