collection vs leaf litter

collection

noun
  • A set of items or amount of material procured or gathered together. 

  • A set of college exams generally taken at the start of the term. 

  • A set of sets; used because such a thing is in general too large to comply with the formal definition of a set. 

  • The jurisdiction of a collector of excise. 

  • The activity of collecting. 

  • Multiple related objects associated as a group. 

  • The quality of being collected; calm composure. 

  • A gathering of money for charitable or other purposes, as by passing a contribution box for donations. 

  • Debt collection. 

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. 

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