clevis vs coat hanger

clevis

noun
  • A U-shaped coupling having holes at each end, through which a bolt is run; used especially to fit attachments to a tractor or other vehicle as it allows a degree of rotation about the bolt. 

coat hanger

noun
  • A device used to hang up coats, shirts, etc, consisting of a hook with sloping "arms" in the approximate shape of human shoulders. 

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