It's called a delving because dwarves delve there. Try saying that 10 times fast.

The Lord of The Rings Online community site takes a look at one of the new game locations in Book 12 today: The Delving of Frór.

In ages long past, dwarves delved throughout the Misty Mountains and there drew forth precious ore from the land. At the foot of those mountains, beneath the shadow of what is now called Mount Gram, is one such delving - The Delving of Frór.

Read all about it at the LoTRO Community site.