call for help vs fire alarm

call for help

fire alarm

noun
  • An electromechanical or electronic bell, klaxon, chime, horn, speaker, strobe light or other device which warns people in a building of a possible fire or other condition requiring evacuation. 

  • The sound or other warning made by a fire alarm. 

  • An emergency response to a fire by the fire department with manpower and equipment. 

How often have the words call for help and fire alarm occurred in a corpus of books? (source: Google Ngram Viewer )