erstwhile vs former

erstwhile

adj
  • Former, previous. 

  • Respected, honourable. 

former

adj
  • Previous. 

  • First of aforementioned two items. Used with the, often without a noun. 

noun
  • An object used to form something, such as a template, gauge, or cutting die. 

  • Someone who forms something; a maker; a creator or founder. 

  • Someone in, or of, a certain form (class). 

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