Of old, the Lhûn had been a line of defense: first against Sauron, and later against the Witch-king.
In the Third Age, the Lhûn formed the border between Mithlond and Arnor. During the War with Angmar, it formed the end of the Witch-king's influence: many of the Dúnedain fled across it. When Eärnil II came, passage was won back over it. With their defeat imminent, many of the Witch-king's minions drowned in the river Lhûn.
The river Lhûn found its origin in the First Age or before, but following the War of Wrath, its course was severely altered. Its original course is no longer recorded in history, but after the breaking of the Blue Mountains, it flowed in the Gulf of Lhûn. The river had its origin in the north of the Blue Mountains, and had two tributaries: the Little Lune and an unnamed river that had its origin in the Emyn Uial.
The meaning of Lhûn is not known. Originally, Tolkien envisioned it as Noldorin for "blue". Lhûn, and especially the initial /lh/, may have been valid in Noldorin, it was not so in Sindarin, so Tolkien had to rewrite the etymology. He considered the following the following:
- CE Slōna, "floody"
- CE Slōnā, "in flood, full of water" (during melting season)
- CE Slounā, "flow freely"
- CE Slōno, "deep of water, applied originally to the Gulf!"
- A renaming to Sîr Luin, "Blue River"
- CE Slōn, "sound"
- A Khuzdul origin, salôn or sulûn, "fall, descend swiftly"
- ↑ J.R.R. Tolkien, Christopher Tolkien (ed.), Unfinished Tales, "The History of Galadriel and Celeborn", "Concerning Galadriel and Celeborn"
- ↑ J.R.R. Tolkien, The Lord of the Rings, Appendix A, "Eriador, Arnor and the Heirs of Isildur"
- ↑ J.R.R. Tolkien, The Lord of the Rings, Appendix A, "Gondor and the Heirs of Anarion"
- ↑ J.R.R. Tolkien, Christopher Tolkien (ed.), The Silmarillion, "Of the Rings of Power and the Third Age"
- ↑ Patrick H. Wynne, "The Problem of Lhûn", published in Vinyar Tengwar 48 (December 2005)