be serious vs fun

be serious

fun

noun
  • playful, often noisy, activity. 

  • amusement, enjoyment or pleasure 

adj
  • Enjoyable or amusing. 

  • Whimsical or flamboyant. 

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

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