fortuitously vs on accident

fortuitously

adv
  • In a fortuitous manner; in a manner of happening by chance; coincidentally; accidentally. 

  • In a fortuitous manner; in a manner of happening by a lucky chance; luckily; fortunately. 

on accident

adv
  • Accidentally; not intentionally; because of error, misfortune, or lack of caution. 

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