gruff vs surd

gruff

adj
  • hoarse-voiced. 

  • Of goods: bulky. 

  • having a rough, surly, and harsh demeanor and nature. 

verb
  • To speak gruffly. 

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