surd vs unfriendly

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. 

unfriendly

adj
  • Unfavourable. 

  • Not friendly; hostile; mean. 

noun
  • An enemy. 

adv
  • in an unkind or unfriendly manner; not as a friend 

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