adytum vs reredos

adytum

noun
  • A private chamber; a sanctum. 

  • The innermost sanctuary or shrine in a temple, from where oracles were given. 

reredos

noun
  • The back of an open fire-hearth, in medieval halls. 

  • A screen or decoration behind the altar in a church, usually depicting religious iconography or images, akin to the iconostasis of the Eastern Churches. 

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