Mark Metcalfe/Getty Images
The fact that Swift wrote the song was previously kept under wraps so as to not overshadow the music. Swift wrote the hit under the pseudonym "Nils Sjöberg," which has been confirmed by her rep.
Why the name Nils Sjöberg?
It's super random.
While a nod to the popularity of Nordic DJs, there's no real rhyme or reason behind the pen name, at least that we know of yet.
But Nils Sjöberg is in fact a real man in Sweden and he's currently being bombarded by Swifties.
Luckily, he seems to think it's funny. The artist and communications manager tweeted:
"Taylor Swift's fans believe I am @taylorswift13", an unexpected #firstworldproblem #taylorswift #swiftie https://t.co/Xzkl9lKm14
When fans first caught wind that Swift may have actually written the hit track, Sjöberg expressed his emotions through a drawing on his Tumblr account:
There's also a 91-year-old former Swedish gymnast with the name Nils Sjöberg and a poet with the name who died in 1822, but we're pretty sure they're both unrelated to Swift.