chantry vs reredos

chantry

noun
  • A chapel set up for this purpose 

  • An endowment for the maintenance of a priest to sing a daily mass for the souls of specified people 

reredos

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

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

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