fun vs unhappiness

fun

verb
  • To tease, kid, poke fun at, make fun of. 

noun
  • playful, often noisy, activity. 

  • amusement, enjoyment or pleasure 

adj
  • Enjoyable or amusing. 

  • Whimsical or flamboyant. 

unhappiness

noun
  • The feeling of not being happy 

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