pun vs spoonerism

pun

noun
  • A joke or type of wordplay in which similar definitions or sounds of two words or phrases, or different definitions of the same word, are deliberately confused. 

verb
  • To make or tell a pun; to make a play on words. 

  • To beat; strike with force; to ram; to pound, as in a mortar; reduce to powder, to pulverize. 

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 pun and spoonerism occurred in a corpus of books? (source: Google Ngram Viewer )