Did Nicole Richie's Daughter Harlow Change Her Name?

Nicole Richie and Joel Madden’s daughter Harlow Madden is 18!

Richie celebrated the teen’s milestone birthday on Monday, while hinting she may have changed her name.

Nicole posted a carousel of Instagram images with the caption, "18 years of you @katemaddennn.”

If Harlow is going by Kate these days, it would mean she’s chosen to use one of her middle names instead of her first. Her full name is: Harlow Winter Kate Madden.

Her Uncle Benji Madden also referred to her as Kate, posting in the comments, "How to make a grown man cry!!! 😭😭😭😭😭😭😭❤️❤️❤️❤️❤️ love you Kate! You’re a bad ass! Never forget it! Happy 18!! 🎉🎉❤️❤️🎉”

Meanwhile, Joel wrote, "That’s my girl ❤️✨.”

Back in 2008, Nicole and Joel explained to People magazine why they chose her name.

According to Eonline.com, they said Harlow as inspired by actress Jean Harlow and model Shalom Harlow, while Joel said they found the winter season “so serene and quiet.”

As for Kate… Nicole said, "I always liked the name Kate, but I knew I'd never name my kid that because it was just too plain.”

Richie went on to name her jewelry line House of Harlow and her clothing line Winter Kate.

In October, Nicole chatted with “Extra” about sharing clothes with her daughter, who she says has an “effortless and cool” style.

“We’re pretty open with each other and we let each other borrow whatever we want,” she said. “My mom always let me take and borrow anything I wanted so that’s just the attitude we have.”

Nicole and Harlow, however, have different styles.

“She appreciates mine, but it's not hers,” adding, “She's like effortless and cool and just, you know, she's got her own thing going on.”