Preface vs baptism

Preface

noun
  • The part of the liturgy that precedes the main part of the Eucharist 

baptism

noun
  • A Christian sacrament, by which one is received into a church and sometimes given a name, generally involving the candidate to be anointed with or submerged in water. 

  • A similar ceremony of initiation, purification or naming. 

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