at ease vs tranquil

at ease

prep
  • Allowed to refrain from being in rigid formation. 

  • Free of anxiety; not stressed or tense. 

  • In a relaxed position with the feet apart rather than at attention. 

tranquil

adj
  • Calm; without motion or sound. 

  • Free from emotional or mental disturbance. 

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