slaphappy vs weak in the knees

slaphappy

adj
  • In a humorous mood as a result of fatigue; silly from being tired. 

  • Incoherent from being struck; punch drunk. 

  • Irresponsibly free. 

weak in the knees

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