joking vs spoonerism

joking

noun
  • The act of telling or engaging in jokes. 

verb
  • Kidding, trying to fool. 

spoonerism

noun
  • A play on words on a phrase in which the initial (usually consonantal) sounds of two or more of the main words are transposed. 

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