catechumen vs postulant

catechumen

noun
  • A convert to Christianity under instruction before baptism; a young or recent Christian preparing for confirmation. 

postulant

noun
  • A person seeking admission to a religious order. 

  • A person who submits a petition for something; a petitioner. 

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