surd vs unconfessed

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. 

unconfessed

adj
  • Not acknowledged in a confession. 

  • Not having confessed to a priest. 

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