When Nick Jonas surprised fans with his new song, "Area Code" on Twitter during the Labour Day weekend, it truly was surprising. Not just for his fans, but also for his ex, Selena Gomez.

A source close to Selena said that she had absolutely no idea about Nick's references to their relationship. The singer is reportedly surprised that her ex would make a public statement about her in his song, according to Hollywood Life.

If you're wondering what prompted Selena to respond in this manner, take a look at "Area Code" lyrics. Nick sings, "You say I never been good for you / You can't deny I gave it good to you" at 1:13.

Well, we have much evidence to prove that "Area Code" is the singer's response to Selena's "Good For You." And if you thought she wrote the song with Biebs in mind, Nick has a new perspective to offer.

Ever since "Area Code" appeared on his sound cloud, many have speculated if his song has anything to do with with Selena. In fact, twitter was awash with fans talking about his relationship and Nick favourited a few tweets which related "Area Code" to "Good For You."

While Gomez is taken by surprise at Nick's new song, she isn't particularly upset or disheartened. The source told the publication that she herself has used past relationships as inspiration for her songs, and it would be hypocritical of her to slam anyone for doing the same.

"It's the creative right of an artist, and Selena understands that better than anyone," Hollywood Life quoted the source as saying. 

Nick and Selena dated briefly in 2008, and were seen together at the recently held MTV VMAs on Sunday, 31 August. 

Selena Gomez's new album "Revival" is slated for release on Friday, 3 October.