retarded vs short bus

retarded

adj
  • Extremely stupid. 

  • Delayed; delayed in development, hindered; impeded. 

  • Designating a parameter of an electromagnetic field which is adjusted to account for the finite speed of radiation. 

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 retarded and short bus occurred in a corpus of books? (source: Google Ngram Viewer )