Deeping-coomb
From Tolkien Gateway
The deep, well-defended valley in the northern White Mountains that held Helm's Deep and the castle of the Hornburg. The site of an important battle, the Battle of the Hornburg, during the War of the Ring.
Etymology
The name has the sense "the deep valley belonging to the Helm's Deep" to which it led up.[1]
Coomb means "deep valley" as occurs in English place-names in the forms -comb, -cumb, -combe.
