archpriest vs chaplain

archpriest

noun
  • An honorific title applied to a priest who has a specific function. 

  • The highest rank given to a married priest. 

chaplain

noun
  • A member of a religious body who is (often, although not always, of the clergy) officially assigned to provide pastoral care at an institution, group, private chapel, etc. 

  • A person without religious affiliation who carries out similar duties in a secular context. 

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