Briticism vs Britishism

Briticism

noun
  • A word or figure of speech used in Britain exclusively or primarily. 

Britishism

noun
  • A word, phrase, idiom, or expression peculiar to the English language as spoken in Britain. 

  • The practice of British religion or culture. 

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