palpitation vs stillness

palpitation

noun
  • An abnormal beating of the heart that may be perceived by the patient, a result of excitement, exertion, or illness. 

stillness

noun
  • Habitual silence or quiet; taciturnity. 

  • The quality or state of being still. 

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