insensible vs surd

insensible

adj
  • Unable to be understood; unintelligible. 

  • Incapable or deprived of physical sensation. 

  • Unable to be perceived by the senses. 

  • Incapable of mental feeling; indifferent. 

  • Not sensible or reasonable; meaningless. 

  • Incapable of emotional feeling; callous; apathetic. 

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 insensible and surd occurred in a corpus of books? (source: Google Ngram Viewer )