consolidate vs stiffen

consolidate

verb
  • To make stronger or more solid. 

  • With respect to debt, to pay off several debts with a single loan. 

  • To combine into a single unit; to group together or join. 

stiffen

verb
  • To make stiff. 

  • To become stiff. 

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