hummock vs kyphosis

hummock

noun
  • A fistful. 

  • A ridge or hill of ice in an ice field. 

  • A small hill; a hillock; a knoll. 

kyphosis

noun
  • The normal convex curvature of the spine in the thoracic and sacral regions. 

  • An abnormal convex curvature of the spine in the cervical or lumbar regions of the spine. 

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