sad sack vs unsociable

sad sack

noun
  • An incompetent or inept person. 

  • A perennial failure or victim of misfortune. 

unsociable

noun
  • A person who is not sociable. 

adj
  • not congenial or compatible 

  • not desiring the company of others 

  • unfriendly 

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