inquiry vs opinion poll

inquiry

noun
  • The act of inquiring; a seeking of information by asking questions; interrogation; a question or questioning. 

  • Search for truth, information, or knowledge; examination of facts or principles; research; investigation 

opinion poll

noun
  • A poll organized in an attempt to quantify public opinion on a subject. 

How often have the words inquiry and opinion poll occurred in a corpus of books? (source: Google Ngram Viewer )