Christian name vs first name

Christian name

noun

  • Any forename. 

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

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

first name

noun

  • The first element of a full name in cultures that place the given name first. 

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