fetish vs something on the brain

fetish

noun
  • Sexual attraction to or arousal at something abnormally sexual or nonsexual, such as an object or a nonsexual part of the body. 

  • An irrational, or abnormal fixation or preoccupation; an obsession. 

  • Something which is believed to possess, contain, or cause spiritual or magical powers; an amulet or a talisman. 

something on the brain

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