palpitation vs reverberation

palpitation

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

reverberation

noun
  • A violent oscillation or vibration. 

  • The reflection of light or heat; a reflection in, or as though in, a mirror. 

  • An echo, or a series of overlapping echoes. 

  • An evolving series of effects resulting from a particular event; a repercussion. 

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