hypocoristic vs nom de clavier

hypocoristic

noun
  • A nickname, especially one indicating intimacy and formed through a shortening of the original name. 

adj
  • Relating to a nickname, usually indicating intimacy with the person. 

  • Relating to baby talk. 

nom de clavier

noun
  • A pseudonym used in online communications; a handle. 

How often have the words hypocoristic and nom de clavier occurred in a corpus of books? (source: Google Ngram Viewer )