referendum vs voting

referendum

noun
  • A direct popular vote on a proposed law or constitutional amendment. The adposition on is usually used before the related subject of the vote. 

  • An action, choice, etc., which is perceived as passing judgment on another matter. 

voting

noun
  • action of the verb to vote 

adj
  • Having an associated right for the holder to vote as an owner of business. 

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