interrogation mark vs interrogatory

interrogation mark

noun

  • A question mark. 

interrogatory

noun

  • A question; an interrogation. 

  • A formal question submitted to opposing party to answer, generally governed by court rule. 

adj

  • Serving to interrogate; questioning. 

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