diadem vs sovereignty

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. 

sovereignty

noun
  • Of a ruler: supreme authority over all things. 

  • An independent or sovereign territory. 

  • Of a polity: the state of making laws and controlling resources without the coercion of other nations. 

  • Of a person: the liberty to decide one's thoughts and actions. 

  • Excellence, mastery, preeminent efficacy. 

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