clench vs harbor seal

clench

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

  • A tight grip. 

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

verb
  • To close tightly. 

  • To grip or hold fast. 

harbor seal

noun
  • A species of true seals, Phoca vitulina. 

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