Argus River

From Memory Alpha, the free Star Trek reference

The Argus River is a flowing stream of water located on the planet Rigel IV. Carvings of the hill people of the Argus River region are well known.

In 2267, the knife used by Redjac in a number of serial murders on Argelius II came from the hill people of this region. (TOS: "Wolf in the Fold")