prophylactic vs rhythm method

prophylactic

noun
  • A prophylactic condom. 

  • A medicine which preserves or defends against disease; a preventive. 

  • Any device or mechanism intended to prevent harmful consequences. 

adj
  • Serving to prevent or protect against an undesired effect, especially disease or pregnancy 

rhythm method

noun
  • A method of natural birth control that involves counting days of a woman's menstrual cycle in order to determine when sexual intercourse is most or least likely to result in pregnancy. 

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