addition vs initials

addition

noun
  • A title annexed to a person's name to identify him or her more precisely. 

  • The act of adding anything. 

  • The arithmetic operation of adding. 

  • A dot at the right side of a note as an indication that its sound is to be lengthened one half. 

  • Anything that is added. 

  • Something added to a coat of arms, as a mark of honour. 

initials

noun
  • An abbreviation of a person's name, constructed by taking the initial letters of first, last, and sometimes middle name(s). See monogram 

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