The Deeping-coomb was a 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.
The name has the sense "the deep valley belonging to the Helm's Deep" to which it led.
Coomb means "deep valley", occuring in English place-names in the forms -comb, -cumb, -combe.
 See also