martyry vs reredos

martyry

noun
  • A shrine at a site which "bears witness" to a crucial religious event not related to a tomb. 

  • A shrine in honor of a (usually religious, notably Christian) martyr, possibly at his grave. 

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 martyry and reredos occurred in a corpus of books? (source: Google Ngram Viewer )