Hodor

Hodor is a recurring character in Game of Thrones. He is played by guest star Kristian Nairn and débuts in the first episode of the first season, though he does not speak until the fourth episode.

Hodor is a stableboy serving at Winterfell. He is large and slow of wits, but is gentle and loyal to the Stark family. He is only capable of saying one word, Hodor. His real name is Walder.

Season 1
Hodor greets the arrival of King Robert Baratheon with the rest of the Winterfell household. Theon Greyjoy directs Hodor to carry the crippled Bran Stark to the great hall to meet Tyrion Lannister. He holds Bran whilst Tyrion offers to give him the plans for a new kind of saddle that he can ride even in his crippled state. Some weeks later, Hodor bursts into Bran's room with the saddle made from Tyrion's diagram.

Hodor bathes in the hot pool in the godswood and is seen by Osha, who tells Bran that she thinks he must have giants' blood in him.

In the books
In the Song of Ice and Fire novels Hodor is a the great-grandson of Old Nan, the oldest woman in the castle. Hodor's real name is Walder, but he is only capable of speaking the word, "Hodor," and has become named for it. The meaning of the word is unknown.