gloom vs pessimism

gloom

noun
  • A depressing, despondent, or melancholic atmosphere. 

  • Cloudiness or heaviness of mind; melancholy; aspect of sorrow; low spirits; dullness. 

  • A drying oven used in gunpowder manufacture. 

  • Darkness, dimness, or obscurity. 

verb
  • To be dark or gloomy. 

  • To shine or appear obscurely or imperfectly; to glimmer. 

  • To fill with gloom; to make sad, dismal, or sullen. 

  • To look or feel sad, sullen or despondent. 

  • To render gloomy or dark; to obscure; to darken. 

pessimism

noun
  • The condition of being pessimal. 

  • A general belief that bad things will happen. 

  • The doctrine that this world is the worst of all possible worlds. 

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