tremulous vs unsound

tremulous

adj
  • Timid, hesitant; lacking confidence. 

  • Trembling, quivering, or shaking. 

unsound

adj
  • Not good, unreliable. 

  • Not whole, not solid, defective. 

  • Infirm, diseased. 

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