occult vs surd

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. 

surd

adj
  • unvoiced; voiceless 

  • Involving surds, or irrational numbers; not capable of being expressed in rational numbers. 

noun
  • An irrational number, especially one expressed using the √ symbol. 

  • A voiceless consonant. 

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