abbreviature vs initialism

abbreviature

noun
  • A shortened form of a word or phrase, used in place of the whole; an abbreviation. 

  • An abridgment; a compendium; an abstract. 

initialism

noun
  • The process of forming words or terms using initial letters of other words. 

  • A term formed from the initial letters of several words or parts of words, which is itself pronounced letter by letter. 

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