dead calm vs sluggish

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. 

sluggish

adj
  • Having no power to move oneself or itself; inert. 

  • Habitually idle and lazy; slothful; dull; inactive 

  • Exhibiting economic decline, inactivity, slow or subnormal growth. 

  • Characteristic of a sluggard; dull; stupid; tame; simple. 

  • Slow; having little motion. 

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