diadem vs rule

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. 

rule

noun
  • The act of ruling; administration of law; government; empire; authority; control. 

  • A determinate method prescribed for performing any operation and producing a certain result. 

  • A regulating principle. 

  • A ruler; device for measuring, a straightedge, a measure. 

  • A normal condition or state of affairs. 

  • A regulation, law, guideline. 

  • An order regulating the practice of the courts, or an order made between parties to an action or a suit. 

  • A straight line (continuous mark, as made by a pen or the like), especially one lying across a paper as a guide for writing. 

verb
  • To establish or settle by, or as by, a rule; to fix by universal or general consent, or by common practice. 

  • To regulate, be in charge of, make decisions for, reign over. 

  • To decide judicially. 

  • To mark (paper or the like) with rules (lines). 

  • To excel. 

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