couple vs mate

couple

verb
  • To cause (two animals) to copulate, to bring (two animals) together for mating. 

  • To join in sexual intercourse; to copulate. 

  • To join (two things) together, or (one thing) to (another). 

adj
  • Two or (a) small number of. 

noun
  • A small number. 

  • That which joins or links two things together; a bond or tie; a coupler. 

  • A couple-close. 

  • Two partners in a romantic or sexual relationship. 

  • One of the pairs of plates of two metals which compose a voltaic battery, called a voltaic couple or galvanic couple. 

  • Two of the same kind connected or considered together. 

  • A turning effect created by forces that sum to zero in magnitude but produce a non-zero external torque. 

det
  • Two or a few, a small number of. 

mate

verb
  • To introduce (animals) together for the purpose of breeding. 

  • To arrange in matched pairs. 

  • To copulate with. 

  • To match, fit together without space between. 

  • To match oneself against; to oppose as equal; to compete with. 

  • To move (a space shuttle orbiter) onto the back of an aircraft that can carry it. 

  • To come together as companions, comrades, partners, etc. 

  • To copulate. 

  • To marry; to match (a person). 

  • To pair in order to raise offspring. 

  • To fit (objects) together without space between. 

noun
  • Friendly term of address to a stranger, usually male, of similar age. 

  • A technical assistant in certain trades (e.g. gasfitter's mate, plumber's mate); sometimes an apprentice. 

  • A breeding partner. 

  • In naval ranks, a non-commissioned officer or his subordinate (e.g. Boatswain's Mate, Gunner's Mate, Sailmaker's Mate, etc). 

  • The other member of a matched pair of objects. 

  • A ship's officer, subordinate to the master on a commercial ship. 

  • A suitable companion; a match; an equal. 

  • A first mate. 

  • A friend, usually of the same sex. 

  • A fellow, comrade, colleague, partner or someone with whom something is shared, e.g. shipmate, classmate. 

  • The abovementioned plant; the leaves and shoots used for the tea 

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