incurvate vs sunken

incurvate

adj
  • bending inwards. 

  • Curved; bent; crooked. 

verb
  • to have a curved or bent shape; to bend or curve inwards. 

  • To bend (especially inwards); to give a curved shape to. 

sunken

adj
  • Seeming to have fallen deeper back into the face due to tiredness, illness, or old age. 

  • caused, by natural or unnatural means, to be depressed (lower than the surrounding area) or submerged 

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