front slash vs oblique mark

front 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 front slash and oblique mark occurred in a corpus of books? (source: Google Ngram Viewer )