oblique mark vs scratch comma

oblique mark

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

scratch comma

noun
  • Synonym of slash ⟨ / ⟩ in its former use as a form of comma. 

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