agglomeration vs excerption

agglomeration

noun
  • The act or process of collecting in a mass; a heaping together. 

  • State of being collected in a mass; a mass; cluster. 

  • An extended city area comprising the built-up area of a central city and any suburbs linked by continuous urban area. 

  • a mass of large volcanic fragments bonded under heat. 

excerption

noun
  • The act of excerpting or selecting. 

  • That which is selected or gleaned; an extract. 

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