purring vs tweeter

purring

noun
  • A sound that purrs. 

  • Synonym of shin-kicking 

tweeter

noun
  • An electronic speaker designed to produce high-frequency sound. 

  • One who or that which makes a tweeting noise. 

  • One who posts messages ("tweets") on the social networking site Twitter. 

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