The real name of the Game of Thrones character called Hodor is Wylis. The television series reveals his earlier identity through Bran Stark’s visions in the sixth-season episode “The Door.”
As a boy, Wylis could speak normally and worked as a stablehand at Winterfell. A traumatic event involving Bran’s consciousness, the command to “hold the door,” and Wylis’s death causes the phrase to break down into the single word “Hodor.”
Hodor later becomes known for his strength, loyalty, and his role in helping Bran travel after Bran is injured. Although he can say only “Hodor” in the present-day storyline, the flashbacks establish Wylis as his original name in the television adaptation.
The name Walder belongs to the character’s identity in George R. R. Martin’s book series, where the adaptation uses a different name. Because the question specifically asks about the Game of Thrones television character, Wylis is the correct answer.