devotion vs piety

devotion

noun
  • Religious veneration, zeal, or piety. 

  • The act or state of devoting or being devoted. 

  • Feeling of strong or fervent affection; dedication 

  • A prayer (often found in the plural) 

piety

noun
  • A devout act or thought. 

  • Reverence and devotion to God. 

  • A belief that is accepted unthinkingly and with undue reverence. 

  • Similar reverence to one's parents and family or to one's country. 

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