initiatory vs preparatory

initiatory

adj
  • Of or pertaining to initiation 

  • inceptive, initial, inaugural or introductory 

noun
  • An introductory act or rite. 

preparatory

adj
  • Of or pertaining to preparation, having the purpose of making something or someone ready, preparative. 

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