loneliness vs solitariness

loneliness

noun
  • The condition or state of being alone or having no companions. 

  • The state of being unfrequented or devoid of human activity (of a place or time). 

  • A feeling of depression resulting from being alone or from having no companions. 

solitariness

noun
  • The state or quality of being solitary. 

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