Sutherland called his head-mounted display the Sword of Damocles because it had to hang from the ceiling on users’ heads. Without this support, it was heavy enough to crush users. The name is reference to Damocles, a courtier at the court of Dionysus II, ruler of Syracuse.
Legend has it that Dionysus became annoyed at Damocles for always fawning over him, so he allowed Damocles to sit for a time on his throne and see what it was like to be king. Just as Damocles began to enjoy the servants who were waiting on him, he looked up and noticed that Dionysus had hung a sword above his head, suspended only by a strand of horse hair. Fear kept him locked in the throne, afraid to move, until he finally decided that the life of king may in fact be quite precarious.