surd vs voiced

surd

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

  • A voiceless consonant. 

adj
  • unvoiced; voiceless 

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

voiced

adj
  • That contains voice. 

  • Sounded with vibration of the vocal cords. For example, the phone [z] is voiced, while [s] is unvoiced. 

  • Having a specified kind of voice. 

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