done thing vs formality

done thing

noun
  • Something done habitually or according to social norms, expectations, etc. 

formality

noun
  • Something said or done as a matter of form. 

  • A specific requirement for obtaining a legal status, conducting a transaction, etc. 

  • A customary ritual without new or unique meaning. 

  • The state of being formal. 

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