- Erech — ancient M; (hill of the) Pledge; the name could well relate to ÓROK- goblin, Danian [ancient Sylvan Elven tongue] urc, pl. yrc [Etym], since the hill is said in The Return of the King to be overlain by the terror of the Sleepless Dead; it could also relate to ERÉK- thorn [Etym; in its 'Biblical' sense]; in his Letters, Tolkien implicates the Elvish root ER 'alone', although he says it is not the source of the name; the name could be a form of OE wær faith, pledge; reinforcing this last is the Old Norse name 'Erik' - honor of the king, also Early Irish árach 'bail, contract', since it was here the Men of Dunharrow pledged their aid to Isildur; interestingly, in Gaelic the word éirich means rise [hill]; another of the names of this area that had an Elvish sound, but were ancient ['pre-Númenórean'] Mannish; a hill in Lamedon.
In the Second Age, Isildur brought with him a three meter tall stone as a symbol of his lineage and Gondor. He set it on a hill in Erech. He made the local hill tribes swear an oath of loyalty on the stone. The hill tribes later broke their oath and were doomed to haunt the place as the Dead Men.
The city was completely abandoned by the end of the Third Age, when the heir of Isildur, Aragorn, came to Erech to hold the Dead to their oath again. This time they held true to their oath and formed the Host of the Dead to help Aragorn defeat the Corsairs of Umbar at Pelargir.
After the battle at Pelargir, Aragorn released them from their oath and they were allowed to rest.