The most recent episode of Game of Thrones revealed that Hodor was not always Hodor; once upon a time, he was a kind, intelligent boy named Wylis whose vocabulary included much more than a single word.
So how did Wylis turn into the dim-witted (though still kind-hearted) lug known as Hodor? As usual, the Reddit community has tossed around some theories, with one in particular that’s so bizarre, it just might hold some weight.
Redditors TazoGreenTea and Gbinasia have broken down the Winterfell flashback scene from “Home” and come to the conclusion that Wylis was actually a warg like Bran. Their theory holds that since Lyanna Stark is the only character who showed any affection for Wylis, he likely chose to warg into an animal that would enable him to be close to her; namely, Lyanna’s horse. And as Gbinasia explains, this is how Wylis eventually lost his speaking ability and became Hodor:
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.
While this theory does sound like a bit of a stretch, it is thought-provoking. After all, Bran has been warned numerous times throughout the books and TV series not to stay in an animal for too long, lest he lose his human consciousness and become more animal-like. Also, Hodor acts very similar to a horse, with his primary function essentially being to ferry Bran around much like a steed would.
Then again, maybe Wylis just got kicked in the head by a horse and lost the majority of his brain function. That’s at least much less creepy than the idea of Hodor deliberately warging into a creature so that Lyanna could “ride” him. Get it? It’s a sex metaph…yeah, you get it.