polling vs secret ballot

polling

noun
  • the process of voting in an election. 

  • The action of taking a poll. 

  • A technique that continually interrogates a peripheral or service to see if it has data to transfer. 

secret ballot

noun
  • The voting system involving ballots available only at official polling places, prepared at public expense, containing the names of all candidates, and marked in secret at the polling places. 

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