clear one's throat vs cough

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. 

cough

verb
  • To force something out of the throat or lungs by coughing. 

  • To make a noise like a cough. 

  • To push air from the lungs in a quick, noisy explosion. 

noun
  • A sudden, usually noisy expulsion of air from the lungs, often involuntary. 

  • Used to focus attention on a following utterance, often a euphemism or an attribution of blame. 

  • A condition that causes one to cough; a tendency to cough. 

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