clench vs hold lightly

clench

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. 

verb
  • To close tightly. 

  • To grip or hold fast. 

hold lightly

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