elderly vs used-to-be

elderly

adj
  • old; having lived for relatively many years. 

  • Of an object, being old-fashioned or frail due to aging. 

noun
  • An elderly person. 

  • Older people as a whole. 

used-to-be

adj
  • Former, ex-. 

How often have the words elderly and used-to-be occurred in a corpus of books? (source: Google Ngram Viewer )