A great shaggy stableboy of Winterfell, near seven feet tall and pelted with brown hair from crown to wrist, simple of wits and gentle for all his size, whom Osha the wildling reckoned to have a drop of giant's blood in him. The Stark children took him for Hodor because Hodor was the only word he could speak, until Old Nan, his great-grandmother, told them his right name was Walder. His grandfather, Old Nan's son, died in Robert's Rebellion; his father, her grandson, died at the siege of Pyke in Greyjoy's Rebellion; and what remained of the line was the gentle giant who mucked the stables.
After Bran was thrown from the broken tower in 298 AC and woke a cripple, it was Hodor who carried the boy on his back in a wicker basket, up and down the stair of the maester's turret and out into the wolfswood with Summer at their heels. When Theon Greyjoy took Winterfell, Bran and Rickon hid in the crypts with the wildling, Hodor, and the Reeds, then crept out past the ruin Ramsay Bolton left behind it and parted ways: Rickon south to Skagos with Osha, Bran and Hodor north with Meera and Jojen toward the Wall.
Beyond the haunted forest they sheltered in the weirwood cave of the last greenseer, and there, learning the old craft of the children, Bran began to slip his skin into Summer and from Summer into the great hulking body of Hodor as he had once slipped into Hodor's mind in a winter sleep at Queenscrown to hold him quiet from the wildlings. The stableboy who could speak only the one word now found himself, by stretches, ridden by the boy he had carried, and was still alive, so far as any singer south of the Wall yet knew, when the maesters set down what they had of A Dance with Dragons.