flexion vs tautness

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. 

tautness

noun
  • The property of being taut. 

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