diagonal vs sideway

diagonal

adj
  • Having a slanted or oblique direction. 

  • Of or related to the cater-corner (diagonally opposite) legs of a quadruped, whether the front left and back right or front right and back left. 

  • Joining two nonadjacent vertices (of a polygon or polyhedron). 

  • Having slanted or oblique lines or markings. 

noun
  • A line or cut across a fabric at an oblique angle to its sides. 

  • Synonym of slash ⟨/⟩. 

  • A line joining non-adjacent vertices of a polygon. 

  • A line or plane at an oblique angle to another. 

sideway

adj
  • sidelong 

noun
  • A byway. 

  • A footpath near a road. 

adv
  • sideways 

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