backstair vs enigmatic

backstair

adj

  • clandestine, secret or furtive 

noun

  • The backstairs (stairs at the rear of a building). 

enigmatic

adj

  • Pertaining to an enigma. 

  • Defying description. 

  • Mysterious. 

  • Enigmatical. 

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