secret ballot vs suffrage

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. 

suffrage

noun
  • The right or chance to vote, express an opinion, or participate in a decision, especially in a democratic elections. 

  • A vote in deciding a particular question. 

  • Aid, intercession. 

  • Testimony; attestation; witness; approval. 

  • The right of women to vote. 

  • A prayer, for example a prayer offered for the faithful dead. 

  • A short petition, as those after the creed in matins and evensong. 

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