agenda vs agendum

agenda

noun
  • A list of matters to be taken up (as at a meeting). 

  • A notebook used to organize and maintain such plans or lists, an agenda book, an agenda planner. 

  • A temporally organized plan for matters to be attended to. 

  • An ulterior motive. 

agendum

noun
  • Something to be done; a practical duty, rather than an article of faith. 

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