antonym vs counterpart

antonym

noun
  • A word that describes one end of a scale, while its opposite describes the other end, such as large versus small; a gradable antonym. 

  • A word which has the opposite meaning of another word. 

counterpart

noun
  • Either of two parts that fit together, or complement one another. 

  • One who or that which resembles another. 

  • A duplicate of a legal document. 

  • One who or that which has corresponding functions or characteristics. 

  • Either half of a flattened fossil when the rock has split along the plane of the fossil. 

verb
  • To counterbalance. 

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