The fact that Hodor was once able to say words other than "Hodor" wasn't the most discussed plot twist on the latest episode of Game of Thrones, but it was still intriguing as hell. Why would Hodor go from a kindhearted stable boy named Wylis to a severely impaired, gigantic man who mostly just carries Bran around and says "Hodor" with varying degrees of pathos? One fan thinks he knows why: Hodor was once a warg, just like Bran.
Writes user TazoGreenTea on Reddit:
Could Hodor possibly have been a Warg when he was Wylis?
Sorry if this has been mentioned before but I just thought about it this morning as a possible explanation as to what turned Wylis into Hodor. Given that Hodor could speak as a boy, it might be possible that he was once a warg or possibly had the greensight.
The three-eyed Raven once said that he's been following Bran, Meera and Hodor all their lives. Three-Eyed Raven link It's very possible that Wylis had similar visions that Bran had of the three-eyed raven. Wylis may have been more attuned to his abilities especially if his Old Nan told him stories and shared more knowledge about Warging. I'm thinking that Wylis went far beyond the limits of warging which may have mentally damaged him and turned him into Hodor. I remember Jojen Reed warning Bran not to warg for too long or else he'll be trapped and forget he's human. Jojen Bran link
Also, it would make sense that Hodor warged and identified more as a horse, since he was a stable boy. He's also afraid of thunder like horses Hodor thunder link and has carried Bran on his back using a saddle. Hodor carrying Bran pic
Hopefully an explanation is given in the later episodes as to what happened to Wylis.
Now, if Wyllis was a warg, what would he warg into? As a stable boy, it would make sense that his choice would be to warg into a horse since, like dogs, they are docile and are accustomed to his presence. And if the (possibly) only girl treating him nicely was Lyanna, it would make complete sense that this is the horse he would warg into. White is a symbol of purity, innocence, and Wyllis/Hodor is all that. He could warg into that horse so that he gets pet, brushed and generally receive attention no girls would give him. Since Rhaegar and Lyanna would eventually run away from everyone, it also makes sense that they would both be on horses while doing so and Wyllis/Hodor would have been witness to many events of that storyline.
So why would Hodor lose his speaking abilities? My guess is that the horse was slain during battle while Hodor was warging into it, which would explain why he is a very much a simpleton now and is afraid of fighting and lightning. Would also explain why Bran is able to warg into a human, because the mind inside the human is an animal's mind (or the remnant of a mind trapped into a horse). Edit: not necessarily the actual horse's mind, but Hodor's mind mixed with a horse's instint, like Bran feels what Summer feels in his 'dreams'. And, even more obvious, it would explain how Hodor has been such a fantastic person to carry Bran because it's litterally what horses do. Besides, Wylis's demise into Hodor would also serve as an amazing warning to Bran about the dangers of warging, and you can see how the Three Eyed Raven almost interjects when Bran says 'Hodor talks!'. Think about it: wouldn't it be an amazing end to Bran's arc this season? Considering how isolated he is, there are few characters that would make an impact on him. Bran even asks Hodor about what happened to him, and Hodor has no answer but Hodor. For now.
It's convincing, right? But this isn't the only theory. You might prefer this trippy time travel take on things from DustyMuffin:
My feeling is we have already seen show Bran getting very bold, instead of looking from a distance much to the dismay of the raven he ventures closer to his visions of family gone past. Bran will eventually try and communicate or alter history as he knows it, he will not drown from being there too long but his attempts at fixing the past will have dire consequences.
I believe that Bran will see the past as he does, then try and warg into Hordor at the time of one of his green visions. Trying to warg into a past version of Wylis and use his speech to warn someone of the coming danger or how to alter the course of history. As Bran yells and screams inside the head of Wylis to try and get out a warning all that will come from the mouth of Wylis will be 'Hordor.'
Bran will learn the lesson of meddling with the past by being the cause of Hordor's mental state. Showing him that he can not try and fix or warn anyone without causing great harm.
But there are even crazier ideas out there. From Mokey_Maker:
My theory is... Tinfoil warning! Put on your hats! This one is a bit of a stretch but hear me out.
Willis got kicked in the head by a horse and the ensuing brain damage turned him into Hodor.
Wow. Makes you think.