In the last scene of Game of Thrones season 6, the world saw a major fan theory confirmed. That Jon Snow is indeed the son of Rhaegar Targaryen and Lyanna Stark.

But it was only a whisper. Although it was not said out loud, the finale episode in Game of Thrones season 6 confirmed that Jon Snow was indeed the son of Rhaegar Targaryen and Lyanna Stark. Especially after the baby's face then cut into Jon Snow's face.

But he had a name. Jon Snow was not his real name. His last name stemmed from the fact that he was a bastard. If he was born in the desert, his last name would be Sand. Snow is a given name to all the bastards in the North. And Jon was most likely a name Ned Stark came up with in order to keep his identity a secret.

In the scene from the Season 6 finale, we see Lyanna Stark tell her brother Ned, “His name is ...” before the audio conveniently gets quiet and drowned out. Those were most likely her last words.

Maybe the actress did not know his exact name and just mumbled nonsense for the camera. But one Redditor has watched that particular scene multiple times and has found the answer.

The Game of Thrones fan who is a lip reader confirmed that Jon Snow's real name is Jaehaerys. He can make out the first letter of the name which is "J" and then proceeded to syllabicate the rest. Jaehaerys is a name Targaryens have used before, and the Redditor explains it’d make sense since “both previous Jaehaerys to rule were considered good Kings.”

Basing on the HBO clip, only Ned and Lyanna know the real name of Jon Snow. Unless the servants who helped her give birth heard it too. His real name may be revealed in Game of Thrones season 7. 

This is a great time to make a part time career out of lip reading.