appendage vs initials

appendage

noun
  • A part that is joined to something larger. 

  • An external body part that projects from the body. 

  • A natural prolongation or projection from a part of any organism. 

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 appendage and initials occurred in a corpus of books? (source: Google Ngram Viewer )