He will be known as Heritier Lumumba.
O'Brien has always made sure his original first name has featured on official team lists.
Now the player well-known as "Harry O" has dropped the surname of his stepfather Ralph, which he adopted at the age of nine.
"They're already using my last name, Lumumba," O'Brien said of his teammates.
"They're having a lot of fun with it.
"They said `we just can't wait until you get the ball and you're bouncing down the wing and we hear the commentators pronouncing your name'."
Lumumba was born to a Brazilian mother and Congolese father in Rio de Janeiro and moved to Australia when he was three to be raised by his step-parents.
He was the first-born son and said Heritier is a Congolese name meaning inheritor, or the heir.
Lumumba added his surname is famous in the Democratic Republic of the Congo.
"It's a bit stronger than Harry O'Brien ... it's always resonated more with me," the All-Australian defender said.
"This is just the icing on the cake, really."
Lumumba has finished his autobiography after a tumultuous year personally.
He briefly walked out on the club after a disagreement with coach Nathan Buckley, but returned to play out the season.
When he came back to the club, Lumumba said he was dealing with significant personal issues.