Koom Valley

A little more about the URL keyword.

"The inhospitable Koom Valley was home to an ancient battle between dwarfs and trolls that both species came to use as an excuse for their mutual enmity. It was said to be the only known battle in which both sides ambushed the other, and acted as inspiration for the development of the game of Thud."

This vale is thus no different from any of those myriad landscapes which evoke the call to shed blood (again) 'cos that was how it'd happened 50 years back.

"Later engagements have led to a total of sixteen battles of Koom Valley (seventeen counting a "fracas" in Vilinus Pass), only three of which took place in the valley itself. This is in part due to the battle being a convenient patch for rips in time often used by the History Monks, although the History of Thud suggests that something about the valley itself encourages violence (this might be related to the Summoning Dark)."

This is because of quantum. Also, everyone knows mines are dark. But according to Dwarf Lore there are several kinds of Dark. The most fearsome of them all is the Summoning Dark. To a Dwarf, there is no escape from it.

Koom Valley's story is eventually revealed in the novel Thud!.

"The name "Koom" is a reference to the Welsh word cwm, which is pronounced "koom" and means "valley". Thus "Koom Valley" means "Valley Valley." Pratchett has an admitted fondness for tautological place-names, such as "Cheetwood", which literally means "Woodwood," and Torpenhow Hill, which means "Hillhillhill Hill."Now we know. More about Koom Valley later.

Thanks Wiki.