puff up vs thicken

puff up

verb
  • To become proud. (Often written as puffed up with pride.) 

  • To inflate with air. 

  • To swell due to injury or illness. 

  • To fluff up, such as an animal raising its fur or feathers to appear larger or conserve body heat. 

thicken

verb
  • To strengthen; to confirm. 

  • To become thicker (in the sense of wider). 

  • To become thicker (in the sense of more viscous). 

  • To make thicker (in the sense of more viscous). 

  • To make thicker (in the sense of wider). 

  • To make more frequent. 

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