clear one's throat vs expectorate

clear one's throat

verb
  • Forcibly, sometimes mutedly, expelling air from one's lungs, sometimes to clear mucus, sometimes to attract attention to something; less vigorous than coughing. 

expectorate

verb
  • To cough up fluid from the lungs. 

  • To spit. 

How often have the words clear one's throat and expectorate occurred in a corpus of books? (source: Google Ngram Viewer )