diagonal mark vs scratch comma

diagonal mark

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

scratch comma

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

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