crouch vs flexion

crouch

noun
  • A bent or stooped position. 

verb
  • To bend down; to stoop low; to stand close to the ground with legs bent, like an animal when waiting for prey, or someone in fear. 

  • To bend servilely; to bow in reverence or humility. 

flexion

noun
  • The state of being bent or flexed. 

  • Deviation from straightness. 

  • The act of bending a joint, especially a bone joint; the counteraction of extension. 

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