flub vs gaffe

flub

noun
  • An error; a mistake in the performance of an action. 

verb
  • To goof, fumble, or err in the performance of an action. 

gaffe

noun
  • A foolish and embarrassing error, especially one made in public. 

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