adumbration vs datum

adumbration

noun
  • The form of an object as seen by an observer. 

  • The state of being in shadow or shade; (countable) a shadow. 

  • The outline of a charge (“image displayed on an escutcheon”), sometimes filled in with a darker shade than the field. 

  • A rough or symbolic representation; a vague indication of what is to come, a foreshadowing. 

  • A faint sketch; a brief representation, an outline. 

datum

noun
  • A fact known from direct observation. 

  • 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. 

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

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