dispiriting vs saddening

dispiriting

adj
  • Lowering the morale of; making despondent or depressive; disheartening. 

saddening

adj
  • Causing feelings of sadness. 

noun
  • The darkening of a colour during dyeing. 

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