occult vs unidentifiable

occult

adj
  • Secret; hidden from general knowledge; undetected. 

  • Related to the occult; pertaining to mysticism, magic, or astrology. 

  • Esoteric. 

verb
  • To dissimulate, conceal, or obfuscate. 

  • To cover or hide from view. 

noun
  • Supernatural affairs. 

unidentifiable

adj
  • Difficult, if not impossible, to identify or name 

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