datum vs notion

datum

noun
  • A premise from which conclusions are drawn. 

  • A floating reference point, or SLDMB, used to evaluate surface currents in a body of water. Often employed by coastal search and rescue. 

  • A fixed reference point or set of reference points which precisely define a system of measurement or a coordinate system. 

  • A fact known from direct observation. 

verb
  • To provide missing data points by using a mathematical model to extrapolate values that are outside the range of a measuring device. 

notion

noun
  • Inclination; intention; disposition. 

  • Mental apprehension of whatever may be known, thought, or imagined; idea, concept. 

  • A sentiment; an opinion. 

  • An invention; an ingenious device; a knickknack. 

  • Any small article used in sewing and haberdashery, either for attachment to garments or as a tool, such as a button, zipper, or thimble. 

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