pinch off vs writhe

pinch off

verb
  • To separate (something) from something else, using a pinching motion. 

writhe

verb
  • To twist, wring (something). 

  • To twist bodily; to contort one's self; to be distorted. 

  • To extort. 

  • To contort (a part of the body). 

noun
  • A contortion. 

  • The number of negative crossings subtracted from the number of positive crossings in a knot 

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