stretching vs thickening

stretching

noun
  • The act by which something is stretched. 

  • A form of physical exercise in which a specific skeletal muscle (or muscle group) is deliberately elongated to its fullest length in order to improve the muscle's felt elasticity and reaffirm comfortable muscle tone. 

adj
  • Requiring a high level of effort or performance. 

thickening

noun
  • The process of making something, or becoming, thick or viscous. 

  • A thickened part of a structure. 

  • A substance, usually a source of starch, used to thicken a sauce. 

adj
  • Beginning to thicken, becoming thicker. 

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