three-ply vs triplicate

three-ply

noun
  • Yarn having three strands 

adj
  • Having three strands or layers 

triplicate

noun
  • The making of three identical copies of something. 

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

verb
  • To triple. 

  • To make three identical copies of something. 

adj
  • Made thrice as much; threefold; tripled. 

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