gnomon vs pen

gnomon

noun
  • An object such as a pillar or a rod that is used to tell time by the shadow it casts when the sun shines on it, especially the pointer on a sundial. 

  • A plane figure formed by removing a parallelogram from a corner of a larger parallelogram. 

  • An object such as a pillar used by an observer to calculate the meridian altitude of the sun (that is, the altitude of the sun when it reaches the observer's meridian), for the purpose of determining the observer's latitude. 

  • The index of the hour circle of a globe. 

  • A number representing the increment between two figurate numbers (“numbers equal to the numbers of dots in geometric figures formed of dots”). 

pen

noun
  • A light pen. 

  • Penitentiary, i.e. a state or federal prison for convicted felons. 

  • The internal cartilage skeleton of a squid, shaped like a pen. 

  • An enclosure (enclosed area) used to contain domesticated animals, especially sheep or cattle. 

  • A female swan. 

  • Penalty. 

  • A writer, or their style. 

  • The bullpen. 

  • Marks of ink left by a pen. 

  • A wing. 

  • A tool, originally made from a feather but now usually a small tubular instrument, containing ink used to write or make marks. 

verb
  • To enclose in a pen. 

  • To write (an article, a book, etc.). 

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