The character experienced an entire arc that took him from stealing The Sovereign’s Anulax Batteries to his battles with The Ravagers to making friends with the now-deceased Yondu (Michael Rooker) in the latter half of the story.
According to James Gunn’s post, somewhere along the way, the film dropped a reference to Rocket’s early years that didn’t necessarily have much bearing over Vol. 2’s plot but went a long way towards indicating where he came from in the cosmos.
That’s about as vague as vague gets, but it at least it clues us into the fact that Rocket’s origin story received a nod during the most recent installment in the Guardians of the Galaxy franchise.