duad vs helpmate

duad

noun
  • A pair or couple. 

  • Dwadasama. 

  • An unordered pair. 

helpmate

noun
  • A wife or spouse. 

  • A person who supplies help or companionship. 

  • A recreational problem in chess in which both sides cooperate to achieve a specific goal. 

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