derangement vs on the brain

derangement

noun
  • An act or instance of deranging. 

  • A permutation of a set such that no element is in its previous position. 

  • The property of being deranged. 

on the brain

prep
  • Obsessively in mind. 

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