From the One Wiki to Rule Them All, the Lord of the Rings Encyclopedia.
Herugrim was a ancient sword that belonged to
Théoden. He had entrusted the blade to
Grima Wormtongue for "safekeeping", but Grima hid it away and allowed it to rust. When
Gandalf restored Théoden to power, the sword was renewed as well. In
The Two Towers (film) it is adorned with two gleaming horses' heads touching noses above the grip; the book describes it as "a long sword in a scabbard clasped with gold and set with green gems."
Herugrim,the sword of Theoden