divagation vs radiation

divagation

noun
  • Incoherent or wandering speech and thought. 

  • Straying off from a course or way. 

radiation

noun
  • The transfer of energy via radiation. 

  • The shooting forth of anything from a point or surface, like diverging rays of light. 

  • The process of radiating waves or particles. 

  • A rapid diversification of an ancestral species into many new forms. 

  • Radioactive energy. 

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