grow vs untighten

grow

verb
  • To appear or sprout. 

  • To become larger, to increase in magnitude. 

  • To undergo growth; to be present (somewhere) 

  • To develop, to mature. 

  • To cause or allow something to become bigger, especially to cultivate plants. 

  • To assume a condition or quality over time. 

untighten

verb
  • To loosen; to make something less tight. 

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