chaplet vs diadem

chaplet

noun
  • A garland or circlet for the head. 

  • A set of repetitive prayers, other than the Rosary, typically prayed with a string of beads. 

  • The Chaplet of Divine Mercy, the most well-known chaplet in the Catholic Church. 

  • A metal support for a cylindrical pipe. 

  • A molding in the form of a string of beads; a bead molding. 

  • A small chapel or shrine. 

  • A bent piece of sheet iron, or a pin with thin plates on its ends, for holding a core in place in the mould. 

  • A headdress in the form of a wreath made of leaves, flowers or twigs woven into a ring. 

diadem

noun
  • An ornamental headband worn as a badge of royalty. 

  • Regal power; sovereignty; empire—considered as symbolized by the crown. 

  • A crown. 

  • An arch rising from the rim of a crown (rarely also of a coronet), and uniting with others over its centre. 

verb
  • To adorn with a diadem; to crown. 

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