coronate vs diadem

coronate

verb
  • To crown (a sovereign). 

adj
  • Having a crest or a crownlike appendage. 

  • Having the coronal feathers lengthened or otherwise distinguished. 

  • Having or wearing a crown; crowned. 

  • Girt about the spire with a row of tubercles or spines. 

diadem

verb
  • To adorn with a diadem; to crown. 

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. 

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