bifold vs twinfold

bifold

adj
  • Twofold, double. 

  • Of two kinds. 

noun
  • A wallet, billfold, or carrying case with a single fold, so that it opens like a book. 

  • A door, window, shutter, or divider consisting of two equal panels hinged together so that it opens by folding the panels against each other. 

  • A sheet of paper or cardboard folded in half along a crease down the center. 

  • A crease or turn that causes something to double back on itself. 

twinfold

adj
  • Synonym of twofold 

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