The Game of Thrones season six finale was one of the most jam-packed episodes of the show to date. At long last, the HBO hit series is moving into the end-game, and that means all the pieces must be in place for the show's remaining 13 to 15 episodes.

Among those pieces is the mystery behind key events in the past, namely what happened at the Tower of Joy. Fans already glimpsed the tower and the battle that took place there in a previous flashback via Bran's newfound powers, but it is the show's second visit there that may hold far more significance.

Spoilers for the Game of Thrones season six finale below!

During the season six finale, Bran returns to the past to step inside the Tower of Joy and discovers what Ned finds inside. As has long been predicted by fans, inside was none other than Ned's sister Lyanna Stark, dying in childbirth. In the flashback, viewers see Lyanna hand a newborn baby to her brother, and afterward, Lyanna whispers something into Ned's ear and says the iconic words: "Promise me, Ned."

Fans have long assumed that Lyanna was the mother of Jon. The idea for Ned to have a bastard was out of character, and there have been plenty of hints, both in the books and in the show, that Jon is not Ned's son but rather Lyanna's.

It confirms at least half of a long-held fan theory referred to as "R+L=J." The "L" stands for Lyanna, while the "J" stands for Jon. The "R" stands for Rhaegar Targaryen, the prince who supposedly "kidnapped" Lyanna. Most fans assume Rhaegar to be the father of Jon, making the boy half-Stark and half-Targaryen, and a serious contender for the Iron Throne.

That all being said, the show stops short of confirming the theory entirely. There is no mention of Rhaegar in the flashback. There is, however, another clue that could not only confirm that Jon's father is a Targaryen, but also Jon's Targaryen birth name.

As found on Reddit, one fan has obsessed over the flashback scene, specifically the part where Lyanna whispers into Ned's ear. Though it's extremely quiet, the words "His name is" can be heard in the scene, though the remainder of the sentence is cut off. Reddit user sparkledavisjr, attempting to read Lyanna's lips, believes she goes on to say a name that starts with a J and is three syllables long.

"I'm not a great lip-reader, but I'm fairly certain what she says is Jaehaerys," sparkledavisjr writes. "The name is not included in the captions, probably on purpose."

Jaehaerys would make perfect sense. Two previous Targaryen kings shared the name, and the reign of Jaehaerys I was long and prosperous. He was the king responsible for expanding the Night's Watch, and by many accounts, was the greatest of the Targaryen kings. He facilitated the construction of the Kingsroad, restored peace between the Crown and the Faith, improved King's Landing, forbid the tradition of First Night and more.

Certainly, Lyanna and Rhaegar naming their son after such a legendary king would be fitting, considering the newborn's claim to the throne. With most of the Targaryens dead or in hiding, Lyanna's son would be the rightful heir to the seven kingdoms.

That is exactly why Lyanna made Ned promise. The details of that promise are still a mystery, but likely, Lyanna told her brother to protect her son and keep him safe. Ned does that, in part, by taking the baby home as his own. Of course, the child could not be referred to as Jaehaerys, so he chose to name the boy Jon, likely after his mentor Jon Arryn.

As far as fan theories go, it's a sound one. Jon's real name, and his real father, will almost certainly be revealed before the end of the series, which is now in its last 13 to 15 episodes. That means viewers can expect to learn the truth sooner rather than later, but thanks to some dedicated fans, the truth may already have been revealed.