footstool vs prie-dieu

footstool

noun
  • A low stool for supporting the feet while seated. 

  • Anything trodden upon or treated as subservient. 

prie-dieu

noun
  • A piece of furniture on which someone can pray, consisting of a cushioned area to kneel on, with a built-in ledge for books. 

How often have the words footstool and prie-dieu occurred in a corpus of books? (source: Google Ngram Viewer )