caption vs exord

caption

noun
  • The descriptive heading or title, of a document or part thereof. 

  • The section on an official paper (for example, as part of a seizure or capture) that describes when, where, and what was taken, found or executed, and who authorized the act. 

  • A title or brief explanation attached to an illustration, cartoon, user interface element, etc. 

  • A piece of text appearing on screen as a subtitle or other part of a film or broadcast, describing dialogue (and sometimes other sound) for viewers who cannot hear. 

verb
  • To add captions to a text or illustration. 

  • To add captions to a film or broadcast. 

exord

noun
  • A preface or prefatory passage 

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