diagonal mark vs horizontal bar

diagonal mark

noun
  • Synonym of slash as the forward slash ⟨/⟩ and sometimes also its proscribed sense inclusive of the backslash ⟨\⟩. 

horizontal bar

noun
  • The dash symbol (―) (used to introduce quoted text) 

  • The horizontal form of the fraction bar. 

  • A horizontally-aligned bar used in gymnastics, upon which acts of swinging are performed. 

  • A gymnastics event using the horizontal bar. 

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