backstairs vs covert baron

backstairs

adj
  • Secret or furtive. 

  • Scandalous. 

noun
  • An indirect or furtive means of access or intercourse. 

  • A staircase at the rear of a building or one normally only used by servants and tradesmen. 

covert baron

adj
  • Covert, under coverture; married. 

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