announcement vs vocative

announcement

noun
  • An act of announcing, or giving notice. 

  • That which conveys what is announced. 

  • The content which is announced. 

vocative

noun
  • Something said to (or as though to) a particular person or thing; an entreaty, an invocation. 

  • The vocative case 

  • A word in the vocative case 

adj
  • Of or pertaining to calling; used in calling or vocation. 

  • Used in address; appellative (said of that case or form of the noun, pronoun, or adjective, in which a person or thing is addressed). For example "Domine, O Lord" 

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