derailment vs prang

derailment

noun
  • A pattern of discourse (in speech or writing) that is a sequence of unrelated or only remotely related ideas. 

  • The action of a locomotive or train leaving the rails along which it runs. 

  • An instance of diverting a conversation or debate from its original topic. 

prang

verb
  • To crash; to have an accident while controlling a vehicle. 

  • To damage (the vehicle one is driving) in an accident; to have a minor collision with (another motor vehicle). 

noun
  • A type of tower or spire featured in some Buddhist temples of Cambodia and Thailand. 

  • An accident involving a motor vehicle, typically minor and without casualties. 

  • Crack cocaine. 

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