Tattoo enthusiast Harry Styles might have added the initials of rumored new girlfriend Nadine Leopold to his extensive body art collection for 21st birthday.

Styles has a tiny capital letter "A" on his left elbow bend as a tribute to his mother Anne Cox and his older sister's name "Gemma" inked in Hebrew on the upper part of his left arm.

According to The Daily Star, the One Direction member secretly got a brand new ink inspired by the Victoria's Secret model over the weekend, done by his go-to tattooist in Los Angeles. 

"Harry made everyone sign confidentiality agreements so the girl's letters are a secret at the moment," a source close to Shamrock Tattoo Company revealed. "But he had two sets of initials together -- 'HS' is one of them of course, but everyone's saying that the other initials are 'NL' -- for Nadine Leopold."

Also, Styles allegedly requested the tattooist come to his house in order to keep the inking process private.

"Harry used to go to tattoo parlors when he came to L.A.," the source added. "But he gets mobbed so much that he has an artist go to his house instead."

Meanwhile, The Sun (via Mirror) recently reported that Leopold made Styles' star-studded birthday bash even more special.

"Everyone's teasing him, saying he's in love, and he's not denying it. It's the real deal," an insider said. "He's never felt this way about anyone before. Harry has spent virtually all his free time in Los Angeles with Nadine. They're infatuated with each other and can't stand being apart ... there's nobody else he'd rather be with on his birthday."

Styles was apparently able to have a blast while not inviting his ex-girlfriend Taylor Swift.

"She was never invited because he wanted to have fun and inviting drama and all the nonsense she would bring is never fun. Why bring oil in a party full of water?" a source told HollywoodLife.com. "She would want to be the center of attention, and it was his birthday. He wants to be the master of ceremonies, so to speak. He doesn't want to babysit her and have to watch who she is talking to."