airheaded vs short bus

airheaded

adj
  • silly, foolish 

  • unintelligent 

short bus

adj
  • Stupid; dumb; slow. 

noun
  • A shorter school bus, typically equipped with a wheelchair lift, used for transporting children who are physically disabled or who are being educated in special programs, often for learning disabilities. 

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