primary vs secret ballot

primary

noun
  • A primary election; a preliminary election to select a political candidate of a political party. 

  • A directly driven inductive coil, as in a transformer or induction motor that is magnetically coupled to a secondary 

  • A primary school. 

  • A radar return from an aircraft (or other object) produced solely by the reflection of the radar beam from the aircraft's skin, without additional information from the aircraft's transponder. 

  • Any flight feather attached to the manus (hand) of a bird. 

  • A base or fundamental component; something that is irreducible. 

  • The most massive component of a gravitationally bound system, such as a planet in relation to its satellites. 

  • The first year of grade school. 

  • A primary colour. 

  • Primary site of disease; original location or source of the disease. 

  • The first stage of a thermonuclear weapon, which sets off a fission explosion to help trigger a fusion reaction in the weapon's secondary stage. 

adj
  • Earliest formed; fundamental. 

  • first or earliest in a group or series. 

  • main; principal; chief; placed ahead of others. 

  • Relating to day-to-day care provided by health professionals such as nurses, general practitioners, dentists etc. 

  • Relating to the place where a disorder or disease started to occur. 

  • Illustrating, possessing, or characterized by, some quality or property in the first degree; having undergone the first stage of substitution or replacement. 

verb
  • To challenge (an incumbent sitting politician) for their political party's nomination to run for re-election, through running a challenger campaign in a primary election, especially one that is more ideologically extreme. 

  • To take part in a primary election. 

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 primary and secret ballot occurred in a corpus of books? (source: Google Ngram Viewer )