nonmodifiable vs sessile

nonmodifiable

adj
  • Incapable of being modified; immune to modification. 

sessile

adj
  • Permanently attached to a substrate; not free to move about. 

  • Attached directly by the base; not having an intervening stalk; stalkless. 

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