hammer-headed vs smooth-brained

hammer-headed

adj
  • stupid, ignorant 

  • Having a head in the shape of a hammer 

smooth-brained

adj
  • Stupid, foolish; ignorant. 

  • Lissencephalic; having a brain which lacks convolutions due to malformation. 

  • Having a brain which is naturally smooth in appearance. 

How often have the words hammer-headed and smooth-brained occurred in a corpus of books? (source: Google Ngram Viewer )