by and by vs subsequently

by and by

adv
  • After a short time. 

  • After an indefinite period. 

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

subsequently

adv
  • Following, afterwards in either time or place. 

  • Accordingly, therefore (implying a logical connection or deduction), consequently. 

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