by-book vs sketchbook

by-book

noun
  • A notebook or memorandum book. 

  • A subordinate book containing notes or jottings to be afterward extended in due form. 

sketchbook

noun
  • A book or pad with blank pages for sketching; a sketch pad. 

  • A book of printed sketches. 

How often have the words by-book and sketchbook occurred in a corpus of books? (source: Google Ngram Viewer )