atonement vs propitiation

atonement

noun
  • The reconciliation of God and mankind through the death of Jesus. 

  • Making amends to restore a damaged relationship; expiation. 

propitiation

noun
  • The death of Christ as a basis for the forgiveness of sin. 

  • The act of propitiating; placation, atonement, similar to expiation but with the added concept of appeasement of anger. 

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