erstwhile vs one-time

erstwhile

adj
  • Former, previous. 

  • Respected, honourable. 

one-time

adj
  • Of or pertaining to a specific time in the past. 

  • Occurring or used in a single instance and then never again. 

verb
  • To shoot (the ball or puck) directly from a teammate's pass. 

noun
  • The police. 

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