clench vs tighten

clench

verb
  • To close tightly. 

  • To grip or hold fast. 

noun
  • A tight grip. 

  • A local chapter of the Church of the SubGenius parody religion. 

  • A seal that is applied to formed thin-wall bushings. 

tighten

verb
  • To make tighter. 

  • To raise short-term interest rates. 

  • To make money harder to borrow or obtain. 

  • To become tighter. 

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