half-baked vs off the top of one’s head

half-baked

adj
  • incomplete; (of an idea or scheme) not fully planned or carefully considered, ill-conceived, unsound or badly thought-out; (of a person) foolish or having no common sense. 

  • Used other than figuratively or idiomatically: Partially cooked by heating in an oven. 

off the top of one’s head

How often have the words half-baked and off the top of one’s head occurred in a corpus of books? (source: Google Ngram Viewer )