diadem vs regency

diadem

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

  • A crown. 

  • An ornamental headband worn as a badge of royalty. 

  • 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. 

regency

noun
  • The time during which a regent is in power. 

  • An administrative division ranking below a province in Indonesia. 

  • A system of government that substitutes for the reign of a king or queen when that king or queen becomes unable to rule. 

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