napping vs off one's guard

napping

noun
  • The act of taking a nap or short sleep. 

  • The act or process of raising a nap, as on cloth. 

off one's guard

prep
  • Not on one's guard; inattentive to possible hazards and thus vulnerable. 

How often have the words napping and off one's guard occurred in a corpus of books? (source: Google Ngram Viewer )