thin on the ground vs thinning

thin on the ground

adj
  • scarce, or difficult to find. 

thinning

adj
  • Becoming less thick, dense, or numerous 

noun
  • Wood, leaves, or other plant parts removed during the process of thinning 

  • The action or result of reducing thickness, density, or number 

  • Process of removing plants or parts of plants to facilitate the growth of other plants 

How often have the words thin on the ground and thinning occurred in a corpus of books? (source: Google Ngram Viewer )