frequent vs thin on the ground

frequent

verb
  • To visit often. 

adj
  • Done or occurring often; common. 

  • Occurring at short intervals. 

  • Addicted to any course of conduct; inclined to indulge in any practice; habitual; persistent. 

thin on the ground

adj
  • scarce, or difficult to find. 

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