breathlessness vs shortness of breath

breathlessness

noun
  • Difficult or labored respiration, dyspnea, shortness of breath 

  • The state of being breathless or out of breath. 

shortness of breath

noun
  • difficulty in breathing; dyspnea 

How often have the words breathlessness and shortness of breath occurred in a corpus of books? (source: Google Ngram Viewer )