Christian name vs birth name

Christian name

noun
  • An English given name, particularly for ethnic Chinese who usually have a separate Chinese name. 

  • Any forename. 

  • A first name formally given to a child at a Christian baptism. 

birth name

noun
  • A name chosen for a child at birth, as opposed to a different name used subsequently. 

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