fad vs megrim

fad

noun
  • A phenomenon that becomes popular for a very short time. 

megrim

noun
  • See megrims (“depression; any of various diseases of animals”). 

  • A type of flatfish of the genus Lepidorhombus native to the northeastern Atlantic Ocean; specifically, the Cornish sole, sail-fluke, or whiff (Lepidorhombus whiffiagonis). 

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