billow vs tsunami

billow

noun
  • A large wave, swell, surge, or undulating mass of something, such as water, smoke, fabric or sound 

verb
  • To surge or roll in billows. 

  • To swell out or bulge. 

tsunami

noun
  • A very large and destructive wave, generally caused by a tremendous disturbance in the ocean, such as an undersea earthquake or volcanic eruption. Tsunami are usually a series of waves, or wave train. 

  • A large and generally unstoppable surge. 

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