abridgment vs dissertation

abridgment

noun
  • An epitome or compend, as of a book; a shortened or abridged form; an abbreviation. 

  • The state of being abridged or lessened. 

  • The leaving out of certain portions of a plaintiff's demand, the writ still holding good for the remainder. 

  • The act of abridging; reduction or deprivation 

dissertation

noun
  • A lengthy lecture on a subject; a treatise; a discourse; a sermon. 

  • A formal exposition of a subject, especially a research paper that students write in order to complete the requirements for a doctoral degree in the US and a non-doctoral degree in the UK; a thesis. 

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