by and by vs sometime

by and by

adv
  • After an indefinite period. 

  • After a short time. 

noun
  • Heaven; the hereafter. Usually preceded with "the sweet." 

sometime

adv
  • At an indefinite but stated time in the past or future. 

adj
  • Occasional. 

  • Former, erstwhile; at some previous time. 

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