surd vs useless

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. 

useless

adj
  • Unhelpful, not useful; pointless (of an action). 

  • Unable to do well at a particular task or thing. Useless is mildly insulting. 

  • Without use or possibility to be used. 

  • Good-for-nothing; not dependable. 

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