formality vs usage

formality

noun
  • A customary ritual without new or unique meaning. 

  • Something said or done as a matter of form. 

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

  • The state of being formal. 

usage

noun
  • Custom, tradition. 

  • The established custom of using language; the ways and contexts in which spoken and written words are used, especially by a certain group of people or in a certain region. 

  • A custom or established practice. 

  • The act of using something; use, employment. 

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