elision vs initialism

elision

noun
  • The omission of a letter or syllable between two words or inside a word; sometimes marked with an apostrophe. 

  • The deliberate omission of something. 

  • A different mode or method of operating a computer program. 

initialism

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

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

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