The world has just found out about an unusual tradition between mother and son. In Melbourne, after beating Gael Monfils to reach the quarterfinals, Dominic Thiem confirmed that his mother gets a tattoo for every title he wins. 

Now, the Austrian has picked up 16 titles in his career, but the inking didn't begin until Indian Wells last March. Thiem had gone through a minor title draught by not winning a title from September 2018 to March 2019, with a few early round losses to start the season.

"She said if you win this title here, I'm going to make a tattoo," Thiem told Jim Coureir. "I ended up winning that one."

Thiem would snag the Indian Wells crown with wins over Monfils, Milos Raonic and Roger Federer. He'd capture four more titles in 2019, including Barcelona, Kitzbuhel, Beijing and Vienna. 

For each trophy, Karin Thiem picks a tattoo that is symbolic of the country he won in, so for Indian Wells, she got an eagle feather, and for his Beijing win, a panda. 

What about if he wins his next three matches in Melbourne? 

"For sure a kangaroo," Thiem said. 

The No. 5 seed takes on Rafael Nadal for a spot in the semifinals.