chatelain vs custodian

chatelain

noun
  • Synonym of castellan: the lord of a castle; a caretaker entrusted to oversee a castle for its lord. 

custodian

noun
  • A person entrusted with the custody or care of something or someone; a caretaker or keeper. 

  • a janitor; a cleaner 

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