discursion vs tangent

discursion

noun
  • Ratiocination; step-by-step philosophical reasoning, as opposed to intuition. 

  • Digression. 

tangent

noun
  • A topic nearly unrelated to the main topic, but having a point in common with it. 

  • A function of an angle that gives the ratio of the sine to the cosine, in either the real or complex numbers. Symbols: tan, tg. 

  • A small metal blade in a clavichord that strikes the strings to produce sound. 

  • A straight line touching a curve at a single point without crossing it there. 

  • A visual interaction between two or more lines or edges that creates a perceived relationship between them, often in a way that the artist did not intend. 

adj
  • Straight; not horizontally curved. 

  • Touching a curve at a single point but not crossing it at that point. 

  • Of a topic, only loosely related to a main topic. 

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