Names
Elladan means 'elf-man'. In a letter Tolkien suggested that it should be translated 'elf-Númenórean', recalling the particular heritage of Elrond's family.
Elrohir literally translates as 'elf-horse-lord' ('rohir' comes from the same root as 'rohirrim'), however Tolkien's letters suggest that it should be understood as 'elf-knight'.
Biography
Born in the year III 139, little is known of the lives of the twins until the year III 2509, when they rescued their mother Celebrían after she was taken captive by orcs. When the orcs began to multiply in the Misty Mountains, and to attack the surrounding lands, Elladan and Elrohir joined the Dúnedain (the Northern Rangers) in raids against them.
Before the Fellowship set out from Rivendell, the brothers journeyed far, scouting out the land and preparing the way for the company. When a company of the Dúnedain rode to join Aragorn before the muster of the Rohirrim at Dunharrow, the twins rode with them. Elrohir brought Aragorn a message from Elrond to remember the Paths of the Dead.
They rode with Aragorn, Legolas, Gimli and the Grey Company through the Paths of the Dead. Elladan was the torch-bearer at the rear of the Company. They fought alongside Aragorn at the Battle of Pelennor Fields, and they were among the Captains who rode to the Black Gate to challenge Sauron. In the final battle at the Gate, Elladan and Elrohir stood in the front line to face the bitterest assault from Mordor.
The glimpses that are given of the twins in The Lord of the Rings suggest that they have great courage. After Aragorn, Elrohir is the first to speak in support of Gandalf's plan to ride out against Mordor in order to give Frodo a chance of success. There is also a suggestion that they share some of their father's gifts of healing: Aragorn calls for them to work with him among the wounded after the siege of Gondor.
After Elrond sailed west across the Sea, the brothers remained for some time at Rivendell, where they were joined by Celeborn shortly after the departure of Galadriel. Like Elrond, they were given the choice between elfkind and humankind. Their final fate is unknown. Some believe that because they remained behind after Elrond had left Middle-earth, they must have chosen mortality. However, statements in Tolkien's writings about when and how the choice had to be made are ambiguous. In a letter in 1954, he stated that after Elrond passed over the sea, "Elladan and Elrohir ... delay their choice, and remain for a while". It is possible that because of their mother's suffering, they chose to remain in Middle-earth to hunt down the remaining orcs. It also seems that they were close to Aragorn, their foster brother. But it is also possible that in the end they chose to sail across the sea to be re-united with Elrond and Celebrían.
(Image at the top of this page is my own photomanipulation. For full size version, visit the fan art gallery.)>
