covertness vs purdah

covertness

noun
  • The characteristic of being covert. 

purdah

noun
  • Keeping apart; isolation, seclusion; also, concealment, secrecy. 

  • The period between the announcement of an election or referendum and its conclusion, during which civil servants refrain from making policy announcements or taking actions that could be seen as advantageous to certain candidates in the election. 

  • A curtain, especially one used in some Hindu or Muslim traditions to conceal women from the gaze of people, particularly men and strangers. 

  • A long veil or other attire covering most of the body, worn by women in some Muslim societies. 

  • The situation or system of secluding women from the gaze of people, particularly men and strangers, in some Muslim and Hindu traditions, by using a curtain or screen, and/or wearing a face veil or attire covering most of the body. 

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