surd vs undeniable

surd

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

  • unvoiced; voiceless 

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

  • A voiceless consonant. 

undeniable

adj
  • Irrefutable, or impossible to deny. 

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