reinforcement vs stiffening

reinforcement

noun
  • A thing that reinforces. 

  • The process whereby a behavior with desirable consequences comes to be repeated. 

  • A small round white sticker placed around a punched hole in a piece of paper to prevent the binder's rings from tearing through the paper. 

  • Additional troops or materiel sent to support a military action. 

  • The act, process, or state of reinforcing or being reinforced. 

stiffening

noun
  • An item, material or feature that makes something stiffer. 

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