lay preacher vs parson

lay preacher

noun
  • A person who is not ordained but is appointed to lead Church services in a religious denomination. 

parson

noun
  • A Roman Catholic priest of an independent parish church. 

  • A Protestant minister. 

  • An Anglican cleric having full legal control of a parish under ecclesiastical law; a rector. 

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