insatiable vs unappeasable

insatiable

adj
  • Not satiable; incapable of being satisfied or appeased; very greedy 

noun
  • One who or that which cannot be satiated. 

unappeasable

adj
  • Not able to be appeased or satisfied. 

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