forward slash vs oblique mark

forward slash

noun
  • Synonym of slash ⟨ / ⟩. 

oblique mark

noun
  • Synonym of slash ⟨/⟩, sometimes (generally proscribed) inclusive of similar marks such as the backslash ⟨\⟩. 

How often have the words forward slash and oblique mark occurred in a corpus of books? (source: Google Ngram Viewer )