dilate vs tell why

dilate

verb
  • To speak largely and copiously; to dwell in narration; to enlarge; with "on" or "upon". 

  • To enlarge; to make bigger. 

  • To use a dilator to widen (something, such as a vagina). 

  • To become wider or larger; to expand. 

tell why

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