initials vs to-name

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 

to-name

noun
  • A name added to another name; surname. 

  • A name in addition to the Christian name and surname of an individual, to distinguish him or her from others of the same name and usually indicating descent, place of residence, or some personal quality or attribute. Such to-names are often employed where the same families continually intermarry, and where consequently the same name is common to many individuals. 

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