Copperhead
Copperhead is a prominent massif in the Ramtops above Lancre. The mountain is big but is still small enough to be big enough to have a name, unlike really big mountains.
The Copperhead is settled by several dwarf clans and possibly trolls as well. Dwarfs from Copperhead were the first to migrate to Ankh-Morpork.
Copperhead dwarves have a reputation for being much more friendly to humans and trolls than the more conservative clans mining below Überwald (the Deep-Downers), having had to deal with humans from Lancre in trade for many years, and Ankh-Morpork more recently.
Annotations
The name may be an allusion to the mountain Caradhras in Tolkien's Lord of the Rings, whose name translates roughly as "Ruddyhorn" or "Coppery-peak." In the Roundworld, a "copperhead" is a poisonous snake (Agkistrodon contortrix) native to eastern North America.