singles vs voluntary

singles

adj
  • Of or pertaining to unmarried people. 

noun
  • a game between individual players 

  • Synonym of tubulars 

voluntary

adj
  • Of or relating to voluntarism. 

  • Done, given, or acting of one's own free will. 

  • Done by design or intention; intentional. 

  • Endowed with the power of willing. 

  • Working or done without payment. 

noun
  • A supporter of voluntarism; a voluntarist. 

  • A short piece of music, often having improvisation, played on a solo instrument. 

  • A volunteer. 

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