exord vs preamble

exord

noun
  • A preface or prefatory passage 

preamble

noun
  • A short preliminary statement or remark, especially an explanatory introduction to a formal document or statute. 

  • A syncword. 

verb
  • To speak or write a preamble; to provide a preliminary statement or set of remarks. 

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