saving grace vs strength

saving grace

noun
  • A redeeming quality or factor. 

  • God's grace or blessing, enabling sinners to attain salvation. 

strength

noun
  • A positive attribute. 

  • The intensity of a force or power; potency. 

  • The quality or degree of being strong. 

  • The strongest part of something; that on which confidence or reliance is based. 

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