hypocoristic vs sobriquet

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. 

sobriquet

noun
  • A familiar name for a person or thing; a nickname (sometimes assumed by the person, but often given by others), that is descriptive. 

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