once vs subsequently

once

adv
  • Formerly; during some period in the past. 

  • Multiplied by one: indicating that a number is multiplied by one. 

  • One and only one time. 

conj
  • As soon as; when; after. 

subsequently

adv
  • Following, afterwards in either time or place. 

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

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