diadem vs elderdom

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. 

elderdom

noun
  • Authority; dominion. 

  • Preeminence; superiority. 

  • The role or influence of an elder or elders. 

  • The authority, rule, or office of an elder. 

  • The state of being an elder, or of being older; elderhood. 

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