threefold vs triplicate

threefold

verb
  • To make threefold; to triple. 

adv
  • by a factor of three 

noun
  • An algebraic variety of dimension 3. 

adj
  • triple 

  • three times as great 

triplicate

verb
  • To triple. 

  • To make three identical copies of something. 

noun
  • Each of a set of three identical objects or copies. 

  • The making of three identical copies of something. 

adj
  • Made thrice as much; threefold; tripled. 

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