dead calm vs flatbed

dead calm

adj
  • Completely still with no waves and no wind. 

noun
  • The condition of a perfectly flat sea with no waves and no wind. 

flatbed

adj
  • Having a flat bed. 

verb
  • To transport by flatbed. 

noun
  • A railway freight car with no sides; a flatcar. 

  • A document scanner with a flat bed. 

  • An open freight vehicle with no sides, designed to carry heavy or outsized loads. 

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